diff --git a/README.md b/README.md
index 135456f..f765cf4 100644
--- a/README.md
+++ b/README.md
@@ -19,3 +19,6 @@ Algorithm Library started in this project
 ## May-7 (Tue), 2019
 Decided to start the project
 * go.storeformula.com
+
+## Markup 
+https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet
\ No newline at end of file
diff --git a/connect-database/connect-db.js b/connect-database/connect-db.js
index dc4a3e3..9a05553 100644
--- a/connect-database/connect-db.js
+++ b/connect-database/connect-db.js
@@ -1,4 +1,5 @@
 // How to run : $ node .\connect-db.js
+// make sure if port is correct (windows=5433, mac=5432)
 var Pool = require('pg').Pool;
 var config = {
     host: 'localhost',
diff --git a/connect-database/connect-db.sql b/connect-database/connect-db.sql
index 6fd8ba8..6af100c 100644
--- a/connect-database/connect-db.sql
+++ b/connect-database/connect-db.sql
@@ -44,3 +44,24 @@ insert into students(firstname,lastname, country) values
     ('Simon','Park', 'South Korea'),
     ('Cindy','Kwon', 'North Korea')
 ;
+
+
+/************************************
+ 4) basic command after connection (In Mac)
+************************************/
+
+Simons-Air:bin simonpark$ psql -U postgres -p 5432
+password: connect
+
+--  list DB
+postgres-# \l
+
+-- connect DB
+postgres-# \c {school}
+
+-- list tables
+school-# \dt
+
+-- quit DB
+school-# \q
+
diff --git a/connect-service/cis_service.js b/connect-service/cis_service.js
index 6ad0bd3..507502d 100644
--- a/connect-service/cis_service.js
+++ b/connect-service/cis_service.js
@@ -7,7 +7,7 @@ const express = require('express'),
 
 const morgan = require('morgan')
 const router = require('./db_query');
-const bodyParser = require('body-parser')
+// const bodyParser = require('body-parser')
 
 app.use(function(req, res, next) {
   res.header("Access-Control-Allow-Origin", "*");
@@ -17,8 +17,10 @@ app.use(function(req, res, next) {
 });
 
 app.use(morgan('combined')) // combined , short
-app.use(bodyParser.urlencoded({ extended: false }));
-app.use(bodyParser.json());
+// app.use(bodyParser.urlencoded({ extended: true }));
+// app.use(bodyParser.json());
+app.use(express.urlencoded({extended:false}))
+app.use(express.json())
 app.use(router)
 
 
diff --git a/connect-service/db_query.js b/connect-service/db_query.js
index 13fddda..c7e63d9 100644
--- a/connect-service/db_query.js
+++ b/connect-service/db_query.js
@@ -2,13 +2,14 @@ const express = require('express')
 var pool = require('pg').Pool;
 const router = express.Router()
 
+// make sure if port is correct (windows=5433, mac=5432)
 function getConnection(){
     return pool({
         host: 'localhost',
         user: 'mycampus',
         password: 'mycampus',
         database: 'school',
-        port: '5433',
+        port: '5432',
         connectionList: 10
     
     })
diff --git a/database/mongo/mongo.js b/database/mongo/mongo-command.md
similarity index 61%
rename from database/mongo/mongo.js
rename to database/mongo/mongo-command.md
index 8371c62..11409b7 100644
--- a/database/mongo/mongo.js
+++ b/database/mongo/mongo-command.md
@@ -1,55 +1,35 @@
-// https://www.tutorialspoint.com/mongodb/
 
-// 1) Show DB Systems
-//show dbs
+[mong DB manual](https://docs.mongodb.com/manual/reference/method/db.createUser/)
 
-// admin                              0.000GB
-// config                             0.000GB
-// local                              0.000GB
-// node-mongo-registration-login-api  0.000GB
+1) Create Collection
 
-// 2) Switch to the DB
-//use mycustomers
-
-// switched to db mycustomers
- db
-// mycustomers
-
-// 3) Create User
-// db.createUser({
-// ... user:"simon",
-// ... pwd:"1234",
-// ...  roles: [ "readWrite", "dbAdmin" ]
-// ... });
-// https://docs.mongodb.com/manual/reference/method/db.createUser/
-
-// Successfully added user: { "user" : "simon", "roles" : [ "readWrite", "dbAdmin" ] }
-
-// 4) Create Collection
+```
 db.createCollection('customers');
 // { "ok" : 1 }
+```
 
-// 5) Show Collections
-// show collections
-
-// customers
+2) Show Collections
 
+```
 db.customers.insert({first_name:"John",last_name:"Doe"});
 // WriteResult({ "nInserted" : 1 })
+```
 
+3) search Document
+```
 db.customers.find();
 // { "_id" : ObjectId("5c06ec2a49f099d2326ecad1"), "first_name" : "John", "last_name" : "Doe" }
+```
 
-db.customers.find();
-// { "_id" : ObjectId("5c06ec2a49f099d2326ecad1"), "first_name" : "John", "last_name" : "Doe" }
-
-//show collections
-// customers
-// people
+```
 db.people.find();
 // { "_id" : ObjectId("5c06ec582a88942510eb20ae"), "firstname" : "John", "lastname" : "Doe", "address" : "330 Bay St. Toronto", "__v" : 0 }
 // { "_id" : ObjectId("5c06ec582a88942510eb20af"), "firstname" : "Jane", "lastname" : "Doe", "address" : "555 Main St.", "__v" : 0 }
+```
+4) insert Document
+```
 db.customers.insert([{first_name:"Steve", last_name:"Simth"},{first_name:"John",last_name:"Johnson",gender:"female"}]);
+
 // BulkWriteResult({
 //         "writeErrors" : [ ],
 //         "writeConcernErrors" : [ ],
@@ -60,10 +40,13 @@ db.customers.insert([{first_name:"Steve", last_name:"Simth"},{first_name:"John",
 //         "nRemoved" : 0,
 //         "upserted" : [ ]
 // })
+
+```
+
+5) Examples
+```
+
 db.customers.find();
-// { "_id" : ObjectId("5c06ec2a49f099d2326ecad1"), "first_name" : "John", "last_name" : "Doe" }
-// { "_id" : ObjectId("5c06ed5749f099d2326ecad2"), "first_name" : "Steve", "last_name" : "Simth" }
-// { "_id" : ObjectId("5c06ed5749f099d2326ecad3"), "first_name" : "John", "last_name" : "Johnson", "gender" : "female" }
 db.customers.find().pretty();
 db.customers.find().sort({last_name:1});  // ascending
 db.customers.find().sort({last_name:-1}); // descending
@@ -91,5 +74,4 @@ db.customers.find({first_name:"Steve"});
 db.customers.find({$or:[{first_name:"Steve"},{last_name:"Doe"}]});
 
 db.customers.find({"address.city":"Boston"});
-
-
+```
diff --git a/database/mongo/mongo-general.md b/database/mongo/mongo-general.md
new file mode 100644
index 0000000..f772c3b
--- /dev/null
+++ b/database/mongo/mongo-general.md
@@ -0,0 +1,39 @@
+# start mongo DB
+
+1) start deamon
+```
+$ cd ~/Documents/dev/mongodb-4.0/bin
+$ ./mongod
+```
+2) start mongo
+```
+$ ./mongo
+> show dbs                     # 
+> use {db_name}                # 
+> show collections             # 
+> db.{collection_name}.find()  #
+
+```
+
+ 3) Create User
+ ```sql
+ db.createUser({
+ user:"simon",
+ pwd:"1234",
+  roles: [ "readWrite", "dbAdmin" ]
+ });
+
+```
+
+4) MongoDB Compass
+
+```
+mongodb://localhost:27017
+```
+
+# reference
+[mongo DB manual](https://docs.mongodb.com/manual/reference/method/db.createUser/)
+
+[mongoose](https://mongoosejs.com/)
+
+[Tutorial Point](https://www.tutorialspoint.com/mongodb/mongodb_delete_document.htm)
\ No newline at end of file
diff --git a/database/mongo/server.js b/database/mongo/server.js
new file mode 100644
index 0000000..cbb35f9
--- /dev/null
+++ b/database/mongo/server.js
@@ -0,0 +1,81 @@
+// how to run : nodemon server.js
+// Node.js (Mongo DB) Tutorial # 9 / 10
+// https://www.youtube.com/watch?v=bxsemcrY4gQ
+// https://www.youtube.com/watch?v=VVGgacjzc2Y
+
+const mongoose = require('mongoose');
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 8080;
+
+// 1) DB connect
+mongoose.connect('mongodb://localhost/cis',{
+    useNewUrlParser: true,
+    useUnifiedTopology: true
+})
+
+mongoose.connection.on('connected', () => {
+    console.log('Mongo DB connected')
+});
+
+// 2) DB schema
+const studentSchema = new mongoose.Schema({
+    firstName: String,
+    lastName: String,
+    staff: String,
+})
+
+
+// 3) DB model
+const studentModel = mongoose.model('student',studentSchema);
+
+app.use(express.json());
+app.use(express.urlencoded({extended:false}));
+
+app.get('/students', (req, res) => {
+    try{
+        console.log('main workflow:');
+        studentModel.find()
+            .then((result) => {
+                console.log(result);
+                res.send(result);
+            })
+            .catch((err) => console.log(err));
+    } catch(err) {
+        console.log('Internal Error:', error);
+    }
+    //Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
+    // res.json() 
+});
+
+app.post('/add', (req, res) => {
+    const data = {
+        firstName: req.body.firstName,
+        lastName: req.body.lastName,
+        staff: req.body.staff
+    };
+    const newStudent = new studentModel(data);
+
+    try {
+        newStudent.save((error) => {
+            if (error) {
+                res.status(500).json({ msg: 'Sorry, internal server errors' });
+                return;
+            }
+            console.log('your data has been saved');
+            return res.json({
+                msg: 'Your data has been saved!!!!!!'
+            });
+        });
+    
+    } catch(err){
+        console.error(err.message);
+    }
+});
+
+// Run service
+app.listen(port, () => {
+    console.log('Mongo DB started on: ' + port);
+});
+
diff --git a/database/mongo/version1/server1.js b/database/mongo/version1/server1.js
new file mode 100644
index 0000000..6bf77cd
--- /dev/null
+++ b/database/mongo/version1/server1.js
@@ -0,0 +1,59 @@
+// how to run : nodemon server.js
+
+const express = require('express');
+const mongoose = require('mongoose');
+
+const app = express();
+const port = process.env.PORT || 8080;
+
+mongoose.connect('mongodb://localhost/mern',{
+    useNewUrlParser: true,
+    useUnifiedTopology: true
+})
+
+mongoose.connection.on('connected', () => {
+    console.log('Mongo DB connected')
+});
+
+// schema
+const schema = mongoose.Schema;
+const blogSchema = new mongoose.Schema({
+    title: String,
+    body: String,
+    date: {
+        type: String,
+        default: Date.now()
+    }
+})
+
+
+// model
+const blogPost = mongoose.model('blogPost',blogSchema);
+
+const data = {
+    title: "Welcome",
+    body: "Help folks.."
+};
+
+const newBlogPost = new blogPost(data);
+newBlogPost.save((error) => {
+    if(error) {
+        console.log('error');
+    } else {
+        console.log('saved')
+    }
+});
+
+
+app.get('/api', (req, res) => {
+    const data = {
+        username: 'simonpark',
+        age: 5
+    };
+    res.json(data);
+})
+
+app.listen(port, () => {
+    console.log('Mongo DB started on: ' + port);
+});
+
diff --git a/database/mongo/version2/server2.js b/database/mongo/version2/server2.js
new file mode 100644
index 0000000..df3782b
--- /dev/null
+++ b/database/mongo/version2/server2.js
@@ -0,0 +1,64 @@
+// how to run : nodemon server2.js
+
+const mongoose = require('mongoose');
+// const cors = require('cors');
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 8080;
+
+// 1) DB connect
+mongoose.connect('mongodb://localhost/cis',{
+    useNewUrlParser: true,
+    useUnifiedTopology: true
+})
+
+mongoose.connection.on('connected', () => {
+    console.log('Mongo DB connected')
+});
+
+// 2) DB schema
+const schema = mongoose.Schema;
+const blogSchema = new mongoose.Schema({
+    title: String,
+    author: String,
+    body: String,
+    date: {
+        type: String,
+        default: Date.now()
+    }
+})
+
+
+// 3) define DB model
+const blogPost = mongoose.model('blogPost',blogSchema);
+
+
+// if not used, this resource can't be accessed from outside 
+// app.use(cors);
+
+app.use(express.json());
+app.use(express.urlencoded({extended:false}));
+
+app.post("/add", async(req,res) =>{
+    try{
+      console.log("request body:" + req.body.title);
+      res.json("{data: 1}"); // sending {data:1}
+    //   res.send('{data:good}');
+  
+    }catch(err){
+      console.error(err.message);
+    }
+  });
+  
+// dummy get()
+app.get('/', (req, res) => {
+    console.log('listening from : ', req.body)
+    res.send('Hello World-2!\n')
+});
+
+// Run service
+app.listen(port, () => {
+    console.log('Mongo DB started on: ' + port);
+});
+
diff --git a/database/mongo/version3-post/server3.js b/database/mongo/version3-post/server3.js
new file mode 100644
index 0000000..d18acde
--- /dev/null
+++ b/database/mongo/version3-post/server3.js
@@ -0,0 +1,70 @@
+// how to run : nodemon server.js
+// POST method : able to save data into mongoDB
+
+const mongoose = require('mongoose');
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 8080;
+
+// 1) DB connect
+mongoose.connect('mongodb://localhost/cis',{
+    useNewUrlParser: true,
+    useUnifiedTopology: true
+})
+
+mongoose.connection.on('connected', () => {
+    console.log('Mongo DB connected')
+});
+
+// 2) DB schema
+const blogSchema = new mongoose.Schema({
+    title: String,
+    author: String,
+    body: String,
+    date: {
+        type: String,
+        default: Date.now()
+    }
+})
+
+// 3) define DB model
+const blogPost = mongoose.model('blogPost',blogSchema);
+
+
+app.use(express.json());
+app.use(express.urlencoded({extended:false}));
+
+
+// post
+app.post('/add', (req, res) => {
+    const data = {
+        title: req.body.title,
+        author: "spark",
+        body: req.body.body
+    };
+    const newBlogPost = new blogPost(data);
+
+    try {
+        newBlogPost.save((error) => {
+            if (error) {
+                res.status(500).json({ msg: 'Sorry, internal server errors' });
+                return;
+            }
+            console.log('your data has been saved');
+            return res.json({
+                msg: 'Your data has been saved!!!!!!'
+            });
+        });
+    
+    } catch(err){
+        console.error(err.message);
+    }
+});
+
+
+// Run service
+app.listen(port, () => {
+    console.log('Mongo DB started on: ' + port);
+});
+
diff --git a/database/mongo/version4-get/server4.js b/database/mongo/version4-get/server4.js
new file mode 100644
index 0000000..5bfe410
--- /dev/null
+++ b/database/mongo/version4-get/server4.js
@@ -0,0 +1,55 @@
+// how to run : nodemon server.js
+// Node.js (Mongo DB) Tutorial # 9 / 10
+// https://www.youtube.com/watch?v=bxsemcrY4gQ
+// https://www.youtube.com/watch?v=VVGgacjzc2Y
+
+const mongoose = require('mongoose');
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 8080;
+
+// 1) DB connect
+mongoose.connect('mongodb://localhost/cis',{
+    useNewUrlParser: true,
+    useUnifiedTopology: true
+})
+
+mongoose.connection.on('connected', () => {
+    console.log('Mongo DB connected')
+});
+
+// 2) DB schema
+const blogSchema = new mongoose.Schema({
+    title: String,
+    author: String,
+    body: String,
+})
+
+// 3) DB model
+const blogPost = mongoose.model('blogPost',blogSchema);
+
+app.use(express.json());
+app.use(express.urlencoded({extended:false}));
+
+app.get('/students', (req, res) => {
+    try{
+        console.log('main workflow:');
+        blogPost.find()
+            .then((result) => {
+                console.log(result);
+                res.send(result);
+            })
+            .catch((err) => console.log(err));
+    } catch(err) {
+        console.log('Internal Error:', error);
+    }
+    //Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
+    // res.json() 
+});
+
+// Run service
+app.listen(port, () => {
+    console.log('Mongo DB started on: ' + port);
+});
+
diff --git a/document/buildBackendService.md b/document/buildBackendService.md
index c79bfe9..487cf68 100644
--- a/document/buildBackendService.md
+++ b/document/buildBackendService.md
@@ -13,6 +13,7 @@
         - port needs to be updated according to your env. (port:'5433')
     - Step 3: Run the Service
         - $ nodemon cis_service.js
+        - $ npm install -g nodemon     # in order to run 'nodemon' command
 
 
 #### How to run REST API using Postman 
diff --git a/document/buildGit.md b/document/buildGit.md
index c0c16f2..67ba1d4 100644
--- a/document/buildGit.md
+++ b/document/buildGit.md
@@ -1,17 +1,39 @@
 # Command Script for GIT repository
 
+## Create GIT project in the GitHub
+* refer to the google document MyDrive/4_IT/Git
+1) Create repository in the gitHub
+
+2) run the clone
+```
+* $ git clone https://github.com/psean21c/spark
+* $ git push origin HEAD
+```
+3) modify .gitignore file to list of files to be ingored
+
+
+
 ## Create branch before PR(Pull Request)
+```
 $ git checkout -b <your-branch>
 $ git commit -m "added new module to project"
 $ git push origin HEAD
 
-# When you need to update your branch with master (Assume that you are at <your-branch>)
+// below is the sample
+$ git checkout -b mac1
+$ git push origin mac1
+```
+
+## When you need to update your branch with master (Assume that you are at <your-branch>)
+```
 $ git checkout master
 $ git pull
 $ git checkout <your-branch>
 $ git pull origin master
+```
 
-# Git stash/rebase (Assume that you are at <your-branch>)
+## Git stash/rebase (Assume that you are at <your-branch>)
+```
 $ git status
 $ git stash
 $ git checkout master
@@ -19,12 +41,13 @@ $ git pull
 $ git checkout <your-branch>
 $ git rebase master
 $ git stash pop
+```
+
+## Reference
+[VCS-GIT](https://www.git-tower.com/learn/git/ebook/en/command-line/basics/what-is-version-control#start)
 
-# VCS-GIT
-https://www.git-tower.com/learn/git/ebook/en/command-line/basics/what-is-version-control#start
+[Medium : rebase vs. merge](https://medium.com/@checko/merging-two-git-repositories-into-one-preserving-the-git-history-4e20d3fafa4e)
 
-# Medium : rebase vs. merge
-https://medium.com/@checko/merging-two-git-repositories-into-one-preserving-the-git-history-4e20d3fafa4e
+[Jira : rebase vs. merge](https://www.atlassian.com/git/tutorials/merging-vs-rebasing)
 
-# Jira : rebase vs. merge
-https://www.atlassian.com/git/tutorials/merging-vs-rebasing
+[reset revert return](https://opensource.com/article/18/6/git-reset-revert-rebase-commands)
\ No newline at end of file
diff --git a/lab/leetcode/data.txt b/favicon.ico
similarity index 100%
rename from lab/leetcode/data.txt
rename to favicon.ico
diff --git a/lab/aws-2/delete-1.js b/lab/aws-2/delete-1.js
new file mode 100644
index 0000000..8f40bac
--- /dev/null
+++ b/lab/aws-2/delete-1.js
@@ -0,0 +1,65 @@
+/***
+ * API Gateway : 
+ * 1)  Resources / student
+ *      => Resource /{id}
+ *          => Method : DELETE
+
+* 2) Method Request
+
+* 3) Integration Request
+ *   Use Lambda Proxy integration : [checked]
+ * 
+ * Test:
+ *  => {id} :  ce5ccef7-7b59-4a72-98cb-737dfd96b554
+ * 
+ * 
+
+ * 
+ *  ===========================================
+ * Lambda Function:
+ * 1) Add Trigger [API Gateway]
+ * 2) Configuration > Permission
+ *  =>  Create Role 
+ *  => Attach plocies : add [DynamoDB] service
+ * 3) in the code below
+  Key instead of Item in params
+
+
+  https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB/DocumentClient.html
+
+ */
+  const AWS = require('aws-sdk');
+  const docClient = new AWS.DynamoDB.DocumentClient({region: 'us-east-1'});
+  
+  exports.handler = async (event, context, callback) => {
+    
+      const id = event.pathParameters.id;   
+      
+      const params = {
+          TableName: "students",
+          Key: {
+              id: id
+          }
+      }
+  
+      await deleteStudent(params)
+      .then(() =>{
+          callback(null, {
+              statusCode: 201,
+              body: 'successfully deleted!',
+              headers: {
+                  "Access-Control-Allow-Origin": "*"
+              }
+          });
+      }).catch((err) => {
+          console.error(err)
+      })
+  
+  
+  };
+  
+  function deleteStudent(params) {
+      console.log('params=>');
+      return docClient.delete(params).promise();
+  }
+  
\ No newline at end of file
diff --git a/lab/aws-2/read-1.js b/lab/aws-2/read-1.js
new file mode 100644
index 0000000..f3bd767
--- /dev/null
+++ b/lab/aws-2/read-1.js
@@ -0,0 +1,72 @@
+
+/**********************************************
+ * API Gateway : 
+ *  ===========================================
+ * 1)  Resources /student
+ *      => Resource /{id}
+ *          => Method : GET
+
+ * 2) Method Request
+
+ * 3) Integration Request
+ *   Use Lambda Proxy integration : [checked]
+
+ * 4) Test:
+ *  => {id} :  ce5ccef7-7b59-4a72-98cb-737dfd96b554
+ * 
+ * 5) Deploy & Test on Postman
+ * https://k3rx4dln3m.execute-api.us-east-1.amazonaws.com/version2/student/8937cbe4-ac56-4f3a-8baa-10abf2b272fa
+ * 
+ * 
+ *  ===========================================
+ * Lambda Function:
+ *  ===========================================
+ * 1) Add Trigger [API Gateway]
+ * 
+ * 2) Configuration > Permission
+ *  =>  Create Role 
+ *  => Attach plocies : add [DynamoDB] service
+ * 
+ * 3) in the code below
+  Key instead of Item in params
+
+ */
+  const AWS = require('aws-sdk');
+  const docClient = new AWS.DynamoDB.DocumentClient({ region: "us-east-1"}); 
+  
+  exports.handler = async (event, context, callback) => {
+      
+      // console.log('event => ',event)
+      const id = event.pathParameters.id;   
+      
+      let responseBody = "";
+      let statusCode = 0;
+      
+      const params = {
+          TableName: "students",
+          Key: {
+              id: id
+          }
+      }
+  
+      try {
+          const data = await docClient.get(params).promise();
+          responseBody = JSON.stringify(data.Item);
+          statusCode = 200;
+      } catch (err) {
+          responseBody = `Unable to get user data` + err;
+          statusCode = 403;
+      }
+  
+      const response = {
+          statusCode: statusCode,
+          headers: {
+              "myHeader": "test"
+          },
+          body: responseBody
+      }
+  
+    return response;
+  };
+  
+  
\ No newline at end of file
diff --git a/lab/aws-2/save-1.js b/lab/aws-2/save-1.js
new file mode 100644
index 0000000..15150cf
--- /dev/null
+++ b/lab/aws-2/save-1.js
@@ -0,0 +1,36 @@
+const AWS = require('aws-sdk');
+const docClient = new AWS.DynamoDB.DocumentClient({region: 'us-east-1'});
+
+exports.handler = async (event, context, callback) => {
+
+    const requestId = context.awsRequestId;
+    const {firstName, lastName, staff} = JSON.parse(event.body);
+
+    const params = {
+        TableName: "students",
+        Item: {
+            "id": requestId,
+            "firstName": firstName,
+            "lastName": lastName,
+            "staff": staff
+        }
+    }
+    
+    //JSON.stringify(data);
+    await createStudent(params).then(() =>{
+        callback(null, {
+            statusCode: 201,
+            body: 'successfully saved',
+            headers: {
+                "Access-Control-Allow-Origin": "*"
+            }
+        });
+    }).catch((err) => {
+        console.error(err)
+    })
+};
+
+function createStudent(params) {
+    return docClient.put(params).promise();
+}
+
diff --git a/lab/express/db-test/check-db-connect.js b/lab/express/db-test/check-db-connect.js
new file mode 100644
index 0000000..02fc224
--- /dev/null
+++ b/lab/express/db-test/check-db-connect.js
@@ -0,0 +1,21 @@
+// How to run : $ node .\connect-db.js
+// make sure if port is correct (windows=5433, mac=5432)
+var Pool = require('pg').Pool;
+var config = {
+    host: 'localhost',
+    user: 'mycampus',
+    password: 'mycampus',
+    database: 'school',
+    port: '5432'
+
+};
+
+var postgres = new Pool(config);
+
+async function get_hits(){
+    console.log('called');
+    var response = await postgres.query("select * from students");
+    console.log(response.rows);
+}
+
+get_hits();
\ No newline at end of file
diff --git a/lab/express/db-test/node-pg.js b/lab/express/db-test/node-pg.js
new file mode 100644
index 0000000..b78b826
--- /dev/null
+++ b/lab/express/db-test/node-pg.js
@@ -0,0 +1,24 @@
+const { Pool, Client } = require('pg')
+const pool = new Pool({
+    host: 'localhost',
+    user: 'mycampus',
+    password: 'mycampus',
+    database: 'school',
+    port: '5432'
+})
+pool.query('SELECT NOW()', (err, res) => {
+  console.log(err, res)
+  pool.end()
+})
+const client = new Client({
+    host: 'localhost',
+    user: 'mycampus',
+    password: 'mycampus',
+    database: 'school',
+    port: '5432'
+})
+client.connect()
+client.query('SELECT NOW()', (err, res) => {
+  console.log(err, res)
+  client.end()
+})
diff --git a/lab/express/hello-world.js b/lab/express/hello-world.js
new file mode 100644
index 0000000..5c20cc1
--- /dev/null
+++ b/lab/express/hello-world.js
@@ -0,0 +1,14 @@
+// http://expressjs.com/en/starter/basic-routing.html
+// how to run: $ nodemon {service_filename}.js
+
+const express = require('express')
+const app = express()
+const port = 3000
+
+app.get('/', (req, res) => {
+  res.send('Hello World!')
+})
+
+app.listen(port, () => {
+  console.log(`Example app listening at http://localhost:${port}`)
+})
diff --git a/lab/express/service1/pg_query1.js b/lab/express/service1/pg_query1.js
new file mode 100644
index 0000000..8426dc8
--- /dev/null
+++ b/lab/express/service1/pg_query1.js
@@ -0,0 +1,10 @@
+const express = require('express')
+const router = express.Router()
+
+// Dummy router
+router.get('/router', (req,res) => {
+    console.log('1111')
+    res.end()
+})
+
+module.exports = router
\ No newline at end of file
diff --git a/lab/express/service1/server_pg1.js b/lab/express/service1/server_pg1.js
new file mode 100644
index 0000000..b4952b0
--- /dev/null
+++ b/lab/express/service1/server_pg1.js
@@ -0,0 +1,23 @@
+// Objective : apply basic route
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 3000;
+
+// const morgan = require('morgan')
+// app.use(morgan('short')) // combined , short
+
+// var pool = require('pg').Pool;
+
+// var router = require('./pg_query2');
+// app.use(router)
+
+app.get('/', (req, res) => {
+  res.send('Hello World!')
+})
+
+
+app.listen(port, () => {
+    console.log('todo list RESTful API server started on: ' + port);
+});
+
diff --git a/lab/express/service2/server_pg2.js b/lab/express/service2/server_pg2.js
new file mode 100644
index 0000000..15ca71e
--- /dev/null
+++ b/lab/express/service2/server_pg2.js
@@ -0,0 +1,26 @@
+// How to check from client side.
+// example
+// $ curl -X GET -H "Accept: application/json" -H "Content-type: application/json" --url "http://localhost:3000/"
+// $ curl -X GET --url "http://localhost:3000/router"
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 3000;
+
+
+app.get('/router', (req,res) => {
+    console.log('1111')
+    res.send('router \n')
+    res.end()
+})
+
+
+app.get('/', (req, res) => {
+  res.send('Hello World!')
+})
+
+
+app.listen(port, () => {
+    console.log('RESTful API server started on: ' + port);
+});
+
diff --git a/lab/express/service3/pg_query3.js b/lab/express/service3/pg_query3.js
new file mode 100644
index 0000000..41f6456
--- /dev/null
+++ b/lab/express/service3/pg_query3.js
@@ -0,0 +1,15 @@
+const express = require('express')
+const router = express.Router()
+
+// route-1
+router.get('/students/',(req,res) =>{
+    console.log("Fetching all students :[" + req + "]")
+    res.send('you send [' + req.eventNames + ']\n')
+})
+
+// route-2
+router.get('/', (req, res) => {
+    res.send('Hello World!')
+})
+  
+module.exports = router
\ No newline at end of file
diff --git a/lab/express/service3/server_pg3.js b/lab/express/service3/server_pg3.js
new file mode 100644
index 0000000..7bc276c
--- /dev/null
+++ b/lab/express/service3/server_pg3.js
@@ -0,0 +1,17 @@
+// 
+// example
+// $ curl -X GET -H "Accept: application/json" -H "Content-type: application/json" --url "http://localhost:3000/"
+// $ curl -X GET --url "http://localhost:3000/students"
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 3000;
+
+
+var router = require('./pg_query3');
+
+app.use(router)
+app.listen(port, () => {
+    console.log('RESTful API server started on: ' + port);
+});
+
diff --git a/lab/express/service4/pg_query4.js b/lab/express/service4/pg_query4.js
new file mode 100644
index 0000000..cfc9943
--- /dev/null
+++ b/lab/express/service4/pg_query4.js
@@ -0,0 +1,32 @@
+const express = require('express')
+const router = express.Router()
+
+const { Pool, Client } = require('pg')
+
+const client = new Client({
+    host: 'localhost',
+    user: 'mycampus',
+    password: 'mycampus',
+    database: 'school',
+    port: '5432'
+})
+client.connect()
+
+// route-1
+router.get('/students/',(req,res) =>{
+    console.log("Fetching all classes:[" + req + "]")
+    res.send('your ip = ' + req.originalUrl + '\n')
+
+    // const queryString = "SELECT NOW()"
+    const queryString = "SELECT firstname,lastname FROM students"
+    client.query(queryString, (err, res) => {
+        if (err){
+            console.log(err.stack)
+        } else {
+            console.log(res.rowCount)
+            // console.log(res.rows)
+        }
+      })
+})
+
+module.exports = router
\ No newline at end of file
diff --git a/lab/express/service4/server_pg4.js b/lab/express/service4/server_pg4.js
new file mode 100644
index 0000000..aca08f8
--- /dev/null
+++ b/lab/express/service4/server_pg4.js
@@ -0,0 +1,19 @@
+// How to run
+// 1)
+// $ nodemon server_pg4.js
+// 2)
+// $ curl -X GET --url "http://localhost:3030/students"
+// $ curl -X GET -H "Accept: application/json" -H "Content-type: application/json" --url "http://localhost:3030/"
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 3030;
+
+
+var router = require('./pg_query4');
+app.use(router)
+
+app.listen(port, () => {
+    console.log('RESTful API server started on: ' + port);
+});
+
diff --git a/lab/express/service5-add/db5.js b/lab/express/service5-add/db5.js
new file mode 100644
index 0000000..fb5ce6a
--- /dev/null
+++ b/lab/express/service5-add/db5.js
@@ -0,0 +1,13 @@
+//   https://www.youtube.com/watch?v=_Mun4eOOf2Q
+
+const Pool = require("pg").Pool;
+
+const pool = new Pool({
+    host: 'localhost',
+    user: 'mycampus',
+    password: 'mycampus',
+    database: 'school',
+    port: '5432'
+});
+
+module.exports = pool;
\ No newline at end of file
diff --git a/lab/express/service5-add/server_pg5.js b/lab/express/service5-add/server_pg5.js
new file mode 100644
index 0000000..d9fe83f
--- /dev/null
+++ b/lab/express/service5-add/server_pg5.js
@@ -0,0 +1,35 @@
+// How to run
+// 1)
+// $ nodemon server_pg5.js
+// 2)
+// $ curl -X GET --url "http://localhost:3030/add"
+
+const express = require('express');
+const  app = express();
+const  port = process.env.PORT || 3030;
+
+const pool = require("./db5") // DB connection
+
+app.use(express.json()) // request.body
+
+// POST
+app.post("/add", async(req,res) =>{
+  try{
+    console.log("request body:" + req.body);
+    const firstname = "Cindy";
+    const lastname = "Kwon";
+    const country = "Korea";
+    const stmt = "INSERT INTO students(firstname,lastname, country) VALUES($1,$2,$3)";
+    const newTodo = await pool.query(stmt,[firstname,lastname,country]);
+    // res.json(newTodo);
+    res.json(newTodo.rows[0]);
+
+  }catch(err){
+    console.error(err.message);
+  }
+})
+
+app.listen(port, () => {
+    console.log('RESTful API server started on: ' + port);
+});
+
diff --git a/lab/express/service6-cors/cors_server.js b/lab/express/service6-cors/cors_server.js
new file mode 100644
index 0000000..d9578e9
--- /dev/null
+++ b/lab/express/service6-cors/cors_server.js
@@ -0,0 +1,36 @@
+// Objective : CORS issue
+// https://github.com/expressjs/cors
+
+// Access to XMLHttpRequest at 'http://localhost:3000/classes' 
+// from origin 'http://localhost:4201' has been blocked by CORS policy
+// : No 'Access-Control-Allow-Origin' header is present on the requested resource.
+// research : https://jonathanmh.com/how-to-enable-cors-in-express-js-node-js/
+
+// How to run
+// 1)
+// $ nodemon cors_server.js
+// 2)
+// $ curl -X GET --url "http://localhost:3030/students"
+
+
+var express = require('express'),
+  app = express(),
+  port = process.env.PORT || 3030;
+
+
+var router = require('./db6');
+app.use(router)
+
+app.use(function(req, res, next) {
+  // res.header("Access-Control-Allow-Origin", "*");
+  // res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
+  res.json({data:[1,2,3,4]})
+  // next();
+});
+
+
+app.listen(port, () => {
+    console.log('RESTful API server started on: ' + port);
+});
+
+
diff --git a/lab/express/service6-cors/db6.js b/lab/express/service6-cors/db6.js
new file mode 100644
index 0000000..4603997
--- /dev/null
+++ b/lab/express/service6-cors/db6.js
@@ -0,0 +1,37 @@
+const express = require('express')
+const router = express.Router()
+const fetch = require("node-fetch")
+const { Pool, Client } = require('pg')
+
+const client = new Client({
+    host: 'localhost',
+    user: 'mycampus',
+    password: 'mycampus',
+    database: 'school',
+    port: '5432'
+})
+client.connect()
+
+// route-1
+router.get('/students/',(req,res) =>{
+    console.log("Fetching all classes:[" + req + "]")
+    res.send('your ip = ' + req.originalUrl + '\n')
+
+    // fetch("file.json")
+    // .then(response => response.json())
+    // .then(data => {
+    //     console.log(data.sentence)
+    //     document.querySelector("#debug").innerHTML = data.sentence
+    // })
+    const queryString = "SELECT firstname,lastname FROM students"
+    client.query(queryString, (err, res) => {
+        if (err){
+            console.log(err.stack)
+        } else {
+            console.log(res.rowCount + "," + res.rows)
+            console.log(res.rows.values)
+        }
+      })
+})
+
+module.exports = router
\ No newline at end of file
diff --git a/lab/express/service6-cors/file.json b/lab/express/service6-cors/file.json
new file mode 100644
index 0000000..fe859f0
--- /dev/null
+++ b/lab/express/service6-cors/file.json
@@ -0,0 +1,3 @@
+{
+    "sentence":"This is a sample file"
+}
diff --git a/lab/js/callback.js b/lab/js/callback.js
deleted file mode 100644
index bb7e42b..0000000
--- a/lab/js/callback.js
+++ /dev/null
@@ -1,143 +0,0 @@
-// Closure vs. Callback
-// Callback function: 
-/**
- * 
- - a function you give to another function, to be run when the other function is finished.
- - a function passed to some other function, which we assume will be invoded at some point
- * */
-
-// so .. the function you call (invoke), calls back by calling the function you gave it when it finishes.
-
-// function sayHi() {
-//     var greet = 'Hi';
-//     setTimeout(function(){
-//         console.log(greet);
-//     }, 3000);
-//     console.log('Also done');
-// }
-
-// sayHi();
-
-// function tellMeWhenDone(callback2) {
-//     var a = 1000;
-//     var b = 2000;
-//     callback2();
-// }
-
-// tellMeWhenDone(function(){
-//     console.log('I am done');
-// });
-    
-
-// tellMeWhenDone(function(){
-//     console.log('All done');
-// });
-
-/*** 
- * 
-// Closure .. 
-function createCounter() {
-    let counter = 1
-    const myFunction = function() {
-      counter = counter + 1
-      return counter
-    }
-    return myFunction
-  }
-  const increment = createCounter()
-  const c1 = increment()
-  const c2 = increment()
-  const c3 = increment()
-  console.log('example increment', c1, c2, c3)
- 
-  
-// Callback
-
-function callF () {
-    var arr = [];
-
-    for(var i=0;i<3;i++){
-        arr.push(function() {
-            console.log(i);
-        })
-    }
-
-    return arr;
-}
-
-var fs = callF();
-fs[0]();
-fs[1]();
-fs[2]();
-
-// result ? 
-// 3 3 3
-
-// Global Execution Context vs. Execution Context
-
-// // Solution-1
-// function callF2 () {
-//     var arr = [];
-
-//     for(var i=0;i<3;i++){
-//         let j = i;
-//         arr.push(function() {
-//             console.log(j);
-//         })
-//     }
-
-//     return arr;
-// }
-
-// var fs2 = callF2();
-// fs2[0]();
-// fs2[1]();
-// fs2[2]();
-
-
-// Solution-2
-function callF3 () {
-    var arr = [];
-
-    for(var i=0;i<3;i++){
-        let j = i;
-        arr.push(
-            (function(j){
-                return function(){
-                    console.log(j);
-                }
-            }(i))
-        );
-    }
-
-    return arr;
-}
-
-var fs3 = callF3();
-fs3[0]();
-fs3[1]();
-fs3[2]();
-
-
-*/
-
-let c = 4
-const addX = x => n => n + x
-const addThree = addX(3)
-let d = addThree(c)
-console.log('example partial application', d)
-
-let c2 = 4
-function addX2(x) {
-  return function(n) {
-     return n + x
-  }
-}
-const addThree2 = addX2(3)
-let d2 = addThree(c2)
-console.log('example partial application', d2)
-
-
-const addY = y;
-const addFour = addY(4);
-console.log(addFour);
\ No newline at end of file
diff --git a/lab/js/callback1.js b/lab/js/callback1.js
deleted file mode 100644
index 87a9a1f..0000000
--- a/lab/js/callback1.js
+++ /dev/null
@@ -1,86 +0,0 @@
-// Closure vs. Callback
-// Callback function: 
-/**
- * 
- - a function you give to another function, to be run when the other function is finished.
- - a function passed to some other function, which we assume will be invoded at some point
- * */
-
-// so .. the function you call (invoke), calls back by calling the function you gave it when it finishes.
-
-
- 
-  
-// Callback
-
-function callF () {
-    var arr = [];
-
-    for(var i=0;i<3;i++){
-        arr.push(function() {
-            console.log(i);
-        })
-    }
-
-    return arr;
-}
-
-var fs = callF();
-fs[0]();
-fs[1]();
-fs[2]();
-
-
-// result ? 
-// 3 3 3
-
-// Global Execution Context vs. Execution Context
-
-// Solution-1
-function callF2 () {
-    var arr = [];
-
-    for(var i=0;i<3;i++){
-        let j = i;
-        arr.push(function() {
-            console.log(j);
-        })
-    }
-
-    return arr;
-}
-
-var fs2 = callF2();
-// fs2[0]();
-// fs2[1]();
-// fs2[2]();
-
-callF2()[0]();
-callF2()[1]();
-callF2()[2]();
-
-
-// Solution-2
-function callF3 () {
-    var arr = [];
-
-    for(var i=0;i<3;i++){
-        let j = i;
-        arr.push(
-            (function(j){
-                return function(){
-                    console.log(j);
-                }
-            }(i))
-        );
-    }
-
-    return arr;
-}
-
-var fs3 = callF3();
-fs3[0]();
-fs3[1]();
-fs3[2]();
-
-
diff --git a/lab/js/data.js b/lab/js/data.js
deleted file mode 100644
index 24399c9..0000000
--- a/lab/js/data.js
+++ /dev/null
@@ -1,15 +0,0 @@
-module.exports = {
-    sum: function (a, b) {
-        return a + b
-    },
-    multiply: function (a, b) {
-        return a * b
-    },
-    ping : function () {
-        console.log("Ping Success");
-    },
-    config: {
-        // console.log('config');
-    }
-};
-// https://stackoverflow.com/questions/5797852/in-node-js-how-do-i-include-functions-from-my-other-files
\ No newline at end of file
diff --git a/lab/js/demo/app.js b/lab/js/demo/app.js
deleted file mode 100644
index 5d9cb9f..0000000
--- a/lab/js/demo/app.js
+++ /dev/null
@@ -1,811 +0,0 @@
-// console.log('start');
-// console.log('end');
-
-// 67-68) strict mode
-// "use strict";
-
-// var person;
-// persom = {}; // Uncaught ReferenceError: persom is not defined
-// console.log(persom);
-
-function logNewPerson() {
-    "use strict";
-    
-    var person2;
-    persom2 = {};
-    console.log(persom2);
-}
-
-var person;
-persom = {};
-console.log(persom);
-logNewPerson();
-
-
-// 66) typeof / instancef
-// var a = 3;
-// console.log('a:' + typeof a);
-
-// var b = "Hello";
-// console.log(typeof b);
-
-// var c = {};
-// console.log(typeof c);
-
-// var d = [];
-// console.log('[]:' + typeof d); // weird!
-// console.log(Object.prototype.toString.call(d)); // better!
-
-// function Person(name) {
-//     this.name = name;
-// }
-
-// var e = new Person('Jane');
-// console.log('e:' + typeof e);
-// console.log(e instanceof Person);
-// console.log('e:' + e instanceof Person);
-
-// console.log(typeof undefined); // makes sense
-// console.log(typeof null); // a bug since, like, forever...
-
-// var z = function() { };
-// console.log('z:'+ typeof z);
-
-// console.log(b instanceof String);
-// console.log('string' instanceof String);
-
-// console.log(a instanceof Number);
-// console.log(1 instanceof Number);
-
-// 65) Initialization
-// var people = [
-//     {
-//         firstname: 'John',
-//         lastname: 'Doe',
-//         addrress: [
-//             '330 Bay St.',
-//             '222 Third St'
-//         ]
-//     },
-//     {
-//         firstname: 'Jane',
-//         lastname: 'Doe',
-//         addrress: [
-//             '123 Bay St.',
-//             '456 Third St'
-//         ],
-//         greet: function(){
-//             return 'Hello';
-//         }
-//     }
-// ]
-
-// $ people[1].greet()
-
-
-// 64) ES6 + classes
-// Syntactic Sugar: A different way to type something ..
-// that doesn't change how it works under the hood..
-
-// class Person{
-//     constructor(firstname, lastname){
-//         this.firstname = firstname;
-//         this.lastname = lastname;
-//     }
-//     greet(){
-//         return 'Hi ' + this.firstname;
-//     }
-// }
-
-// var john = new Person('John','Doe');
-// console.log(john);
-
-// class BadPerson extends Person{
-//     constructor(firstname, lastname){
-//         super(firstname, lastname);
-//     }
-//     greet(){
-//         return 'Yo ' + this.firstname;
-//     }
-// }
-
-// var bad = new BadPerson('Bad','Guy');
-// console.log(bad);
-
-// 63) Object.create / Prototypal inheritance *********************************
-// Polyfill: code that adds a feature which the engine may lack.
-// if(!Object.creat){
-//     Object.create = function(o){
-//         if(this.arguments.length > 1) {
-//             throw new Error('Object.create implementation' + 'only accepts the first parameters.');
-//         }
-//         function F(){}
-//         F.prototype = o;
-//         return new F();
-//     }
-// }
-
-// var person = {
-//     firstname : 'Default First',
-//     lastname : 'Default Last',
-//     greet: function (){
-//         return 'Hi ' + this.firstname;
-//     }
-// }
-
-// var john = Object.create(person);
-// console.log(john);
-// john.firstname = 'John';
-// john.lastname = 'Doe';
-// console.log(john);
-
-
-// 62) arrays / for / in
-// Array.prototype.myCustomerFeature = 'cool';
-
-// var arr = ['John','Jane','Joe'];
-// for(a in arr){
-//     console.log(a + ':' + arr[a]);
-// }
-// console.log('-----------------------');
-
-// // I get extra property, in the case of array, don't use for in
-// for(var i = 0; i< arr.length;i++){
-//     console.log(i + ':' + arr[i]);
-// }
-
-// 60) Built-in function 
-// www.momentjs.com
-
-
-// String.prototype.isLengthGreaterThan = function(limit){
-//     return this.length > limit;
-// }
-
-// console.log("John".isLengthGreaterThan(5));
-
-
-// 57-59) Function Constructor
-// function Person(firstname, lastname) {
-//     console.log(this);
-//     this.firstname = firstname;
-//     this.lastname = lastname;
-//     console.log('This function is invoked');
-//     //return {greeting: 'the way'};
-// }
-
-// Person.prototype.getFullName = function(){
-//     return this.firstname + ' ' + this.lastname;
-// }
-
-// var john = new Person();
-// console.log(john);
-
-// var jane = new Person('Jane','Mill');
-// console.log(jane);
-
-// console.log(jane.getFullName());
-
-// var tony = Person('Tony','Makhoul');
-// console.log(tony);
-
-// 56) reflection
-// var person = {
-//     firstname: 'Default',
-//     lastname: 'Last',
-//     getFullName: function(){
-//         return this.firstname + ' ' + this.lastname;
-//     }
-// }
-
-// var john = {
-//     firstname: 'John',
-//     lastname: 'Doe'
-// }
-
-// john.__proto__ = person;
-
-// // for(var prop in john) {
-// //     //if(john.hasOwnProperty(prop))
-// //     console.log(prop + ' ' + john[prop]);
-// // }
-
-// var jane = {
-//     addrress: '111 Bay St.',
-//     getFullName: function(){
-//         return this.lastname + ' ' + this.firstname;
-//     }
-// }
-
-// var jim = {
-//     getFirstname: function(){
-//         return firstname;
-//     }
-// }
-
-// _.extend(john);//john,jane,jim
-// console.log(john);
-
-
-// 55) Object
-// var a = {};
-// var b = function(){};
-// var c = [];
-
-// a.__proto__
-// b.__proto__.__proto__
-
-
-// 54) Prototype
-// var person = {
-//     firstname: 'Default',
-//     lastname: 'Last',
-//     getFullName: function(){
-//         return this.firstname + ' ' + this.lastname;
-//     }
-// }
-
-// var john = {
-//     firstname: 'John',
-//     lastname: 'Doe'
-// }
-
-// john.__proto__ = person;
-// console.log(john);
-// console.log(john.getFullName());
-// console.log(john.firstname);
-
-// var jane = {
-//     firstname: 'Jane'
-// }
-
-// jane.__proto__ = person;
-// console.log(jane);
-// console.log(jane.getFullName());
-// console.log(jane.firstname);
-
-// 53) Classical vs. Prototype Inheritance
-// Prototypal Inheritance
-
-
-// 51-52) F.P. (Functional Programming) ******************************
-
-// var arr1 = [1,2,3];
-// console.log(arr1);
-
-// var arr2 = [];
-// for(var i=0;i<arr1.length;i++){
-//     arr2.push(arr1[i] *2);
-// }
-
-// console.log(arr2);
-
-// function mapForEach(arr, fn) {
-//     var newArr = [];
-//     for(var i=0;i<arr.length;i++){
-//         newArr.push(
-//             fn(arr[i])
-//         )
-//     };
-//     return newArr;
-// }
-// var arr1 = [1,2,3];
-// var arr2 = mapForEach(arr1, function(item){
-//     return item * 2;
-// });
-
-// var arr3 = mapForEach(arr1, function(item){
-//     return item > 2;
-// });
-// console.log(arr2);
-// console.log(arr3);
-
-// var checkPastLimit = function(limiter,item){
-//     return item > limiter;
-// }
-
-// var arr4 = mapForEach(arr1, checkPastLimit.bind(this,1,0));
-// console.log(arr4);
-
-// var checkPastLimit = function(limiter){
-//     return function(limiter,item){
-//         return item > limiter;
-//     }.bind(this, limiter);
-// };
-
-// var arr5 = mapForEach(arr1, checkPastLimit(2));
-// console.log(arr5);
-
-// http://underscorejs.org
-// lodash.com
-
-// var arr1 = [1,2,3];
-// var arr6 = _.map(arr1, function(item){ return item * 3});
-// console.log(arr6);
-
-// var arr7 = _.filter([2,3,4,5,6,7,8], function(item) {return item %2 ===0});
-// console.log(arr7);
-
-// 50) call, apply, bind, curry ******************************************
-// Function is a special type of object
-// call() , apply(), bind() 
-// name(optional), code
-
-// var person = {
-//     firstname: 'John',
-//     lastname: 'Doe',
-//     getFullName: function() {
-//         var fullname = this.firstname + ' ' + this.lastname;
-//         return fullname;
-//     }
-// }
-
-// var logName = function(lang1, lang2){
-//     console.log('logged:' + this.getFullName);
-//     console.log('arguments:' + lang1 + ' ' + lang2);
-//     console.log('-----------------------');
-// };
-// //.bind(person)
-
-
-// var logPersonName = logName.bind(person);
-// // console.log(logPersonName);
-// // logPersonName();
-
-// logName();
-
-// logPersonName('en');
-
-// logName.call(person,'en','es');
-// //app.js:35 Uncaught TypeError: CreateListFromArrayLike called on non-object
-// //logName.apply(person,'en','es'); 
-// logName.apply(person,['en','es']); 
-
-// // Function Currying
-// // Creating a copy of a function, but with some preset parameters
-// // very useful in mathematical situations
-// function multiple(a,b) {
-//     return a*b ;
-// }
-
-// var multiplebyTwo = multiple.bind(this,2);
-// console.log(multiplebyTwo(5));
-
-
-// 49) Closure + Callback ****************************
-// function sayHiLater(){
-//     var greeting = 'Hi';
-//     setTimeout(function() {
-//         console.log(greeting);
-//     },3000);
-    
-// }
-
-
-// sayHiLater();
-// // jQuery uses function expression and 1st-class functions!
-// // $("button").click(function(){
-
-// // });
-
-// // Callback function:
-// // A function you give to another function, 
-// // to be run when the other function is finished
-// // So the function you call (invoke), 'call back'
-// // by calling the function you gave it when it finishes.
-
-// function callbackDone(callback){
-//     var a = 1000;
-//     var b = 1000;
-//     callback();
-// }
-
-// callbackDone(function(){
-//     console.log('Done1');
-// });
-
-// callbackDone(function(){
-//     // alert('Done2');
-//     console.log('Done2');
-// });
-
-
-
-// 48) Function Factory
-// function makeGreeting(language){
-
-//     return function(firstname, lastname){
-//         if(language ==='en'){
-//             console.log('Hello ' + firstname + ' ' + lastname);
-//         }
-//         if(language ==='ko'){
-//             console.log('An-Niong ' + firstname + ' ' + lastname);
-//         }
-//     }
-// }
-
-// var greetEnglish = makeGreeting('en');
-// var greetKorean = makeGreeting('ko');
-
-// greetEnglish('Simon','Park');
-// greetKorean('Sungmin','Park');
-
-// 46-47) Closure ***********************************
-// function greet(whatever){
-
-//     return function(name){
-//         console.log(whatever + ' ' + name)
-//     }
-// }
-
-// greet('good')('Tony');
-
-// var sayHi = greet('Hi');
-// sayHi('There');
-
-// function buildFun(){
-//     var arr = [];
-//     for(var i=0; i<3;i++){
-//         arr.push(function(){
-//                 console.log(i);
-//         });
-//     }
-//     for(var j=0; j<3;j++){
-//         console.log(j + "" + arr[j]);
-//     }
-
-//     return arr;
-// }
-
-// var fs = buildFun();
-// console.log(fs);
-
-// // fs[0]();
-// // fs[1]();
-// // fs[2]();
-
-// function buildFun2(){
-//     var arr = [];
-//     for(var i=0; i<3;i++){
-//         // 1) use temp variable let
-//         // let j = i;
-//         // arr.push(function(){
-//         //         console.log(j);
-//         // });
-//         // 2) use IIFE
-//         arr.push(
-//             (function(j){
-//                 return function(){
-//                     console.log(j);
-//                 }
-//             })(i)
-//         )
-//     }
-//     return arr;
-// }
-
-// var fs2 = buildFun2();
-
-// fs2[0]();
-// fs2[1]();
-// fs2[2]();
-
-
-
-// 45)
-// (function greet(name){
-//     var greeting = 'Hello';
-//     console.log('Hello ' + name);
-// }('John'));
-
-// console.log(greeting);
-
-// (function greet(global, name){
-//     var greeting = 'Hello';
-//     global.greeting = 'Hello';
-//     console.log(greeting + ' ' + name);
-// }(window,'John'));
-
-// console.log(greeting);
-
-// 44) IIFE (Immediately Invoked Function Expressions) **************
-// function greet(name){
-//     console.log('Hello ' + name);
-// }
-// greet();
-
-// var greetFunc = function(name) {
-//     console.log('Hello ' + name);
-// };
-// greetFunc('haha');
-
-// // using IIFE
-// var greetFunc2 = function(name) {
-//     // console.log('Hello ' + name);
-//     return 'Hello ' + name;
-// }('test');
-
-// console.log(greetFunc);
-// console.log(greetFunc2);
-// // console.log(greetFunc2()); // spark
-// // app.js:20 Uncaught TypeError: greetFunc2 is not a function
-
-// var firstname = 'John';
-// (function(name) {
-//     console.log('IIFE ' + name);
-//     return 'Hello ' + name;
-// }(firstname));
-// (function(name) {
-//     console.log('IIFE-2 ' + name);
-//     return 'Hello ' + name;
-// })(firstname);
-
-// 43) whitespace
-// var firstname, lastname,language;
-
-// var person = {
-//     firstname : 'John',
-//     lastname : 'Doe'
-// }
-
-// console.log(person);
-
-// 42) Automatic Semicolon Insertion
-// function getPerson(){
-//     return 
-//     {
-//         firstname: 'Tony'
-//     }
-// }
-
-// console.log(getPerson());
-
-
-
-// 40) Function overloading
-// function greet(firstname, lastname,language){
-//     language = language || 'en';
-
-//     if(language === 'en') {
-//         console.log('Hello ' + firstname + ' ' + lastname);
-//     }
-
-//     if(language === 'es') {
-//         console.log('Hola ' + firstname + ' ' + lastname);
-//     }
-    
-// }
-
-// greet('John','Doe','en');
-// greet('John','Doe','es');
-
-
-// 39) arguments
-// function greet(firstname, lastname,language = 'en', ... othersss){
-
-//     if(arguments.length ===0) {
-//         console.log('Missing parameters');
-//         return;
-//     }
-//     console.log(firstname);
-//     console.log(lastname);
-//     console.log(language);
-//     console.log(arguments);
-//     console.log('arg0=' + arguments[0]);
-//     console.log('-------------------');
-// }
-
-// greet();
-
-// greet('John');
-// greet('John','Doe');
-// greet('John','Doe','es');
-
-// 38) Array ******
-// var arr = new Array();
-// console.log(arr);
-
-// var arr2 = [
-//     1, 
-//     false, 
-//     'a',
-//     {
-//         name:'Tony',
-//         address: '111 Main St.'
-//     },
-//     function a(name){
-//         var greeting = 'hello';
-//         console.log(greeting + " " +  name);
-//     }
-// ];
-// console.log(arr2);
-// arr2[4]();
-// arr2[4](arr2[3].name); // spark
-
-// 37) this.
-// function a(){
-//     console.log(this);
-//     this.newvariable = 'hello';
-// }
-
-// var b = function () {
-//     console.log(this);
-// }
-
-// a();
-// console.log(newvariable);
-// b();
-
-// var c = {
-//     name: 'The c company',
-//     log: function() {
-//         this.name = 'Updated c company';
-//         console.log(this);
-
-//         var setname = function(newname) {
-//             this.name = newname;
-//         }
-//         setname('Updated again!');
-//         console.log(this);
-//     },
-//     log2: function() {
-//         var self = this;
-//         self.name = 'Updated c company';
-//         console.log(self);
-
-//         var setname = function(newname) {
-//             self.name = newname;
-//         }
-//         setname('Updated again!');
-//         console.log(self);
-//     }    
-// }
-
-// c.log();
-// c.log2();
-
-// 36) by value vs. by reference
-// all primitive types are by value, all objects are by reference..
-// var a = 1;
-// var b = a;
-// a = 3;
-// console.log(a);
-// console.log(b);
-
-// var c = {greeting: 'hi'};
-// var d = c;
-// c.greeting = 'hello'; // mutate
-
-// console.log(c);
-// console.log(d);
-
-// function changeGreeting(obj){
-//     obj.greeting = 'Hola';
-// }
-
-// console.log('----------------------');
-
-// changeGreeting(d);
-// console.log(c);
-// console.log(d);
-
-// console.log('----------------------');
-
-// c = {greeting: 'howdy'};
-// console.log(c);
-// console.log(d);
-
-// 35) F.S. (Function Statement) vs. F.E. (Function Expression)
-// Expression = A unit of code that results in a value,
-// It doesn't have to save to a variable.
-// However, statement does NOT return a value
-// // --------------------------
-// greet();
-
-// // this is statement
-// function greet(){
-//     console.log('hi');
-// }
-
-// //Uncaught TypeError: anonymousGreet is not a function
-// // anonymousGreet();
-
-// // this is expression, 
-// //function expression is not hoisted
-// var anonymousGreet = function() {
-//     console.log('anonymousGreet !!');
-// }
-
-// function log(a){
-//     a();
-// }
-
-
-
-// log(function() {
-//     console.log('what is ?');
-// });
-
-// 34) Function and Object
-// First Class Functions: Assign them to variables, pass them around, 
-// create them on the fly.
-// function greet(){
-//     console.log('hi');
-
-// }
-
-// greet.language = 'english';
-// console.log(greet);
-// console.log(greet.language);
-
-
-// 33) JSON : JavaScript Object Notation
-// var objectLiteral = {
-//     firstName: 'Tony', 
-//     isAProgrammer: true
-// }
-
-// console.log(objectLiteral);
-
-// //console.log(JSON.stringify(objectLiteral));
-
-// var jsonValue = JSON.parse('{ "firstName" : "Mary",    "isAProgrammer": false}');
-// console.log(jsonValue);
-
-// 32) Namespace
-// var greet = 'Hello';
-// var greet = 'Hola';
-
-// var english = {
-//     grettings: {
-//         basic: 'Hello'
-//     }
-// };
-// var spanish = {};
-
-// // english.grettings.greet = 'Hello';
-// // Uncaught TypeError: Cannot set property 'greet' of undefined
-
-// english.greet = 'Hello';
-// spanish.greet = 'Hola';
-
-// console.log(english);
-
-// 30) Object and DOT(.)
-// var person = new Object();
-
-// person["firstname"] = "Tony";
-// person["lastname"] = "Alicea";
-
-// var firstNameProperty = "firstname";
-
-// console.log(person);
-// console.log(person[firstNameProperty]);
-
-// console.log(person.firstname);
-// console.log(person.lastname);
-
-// person.address = new Object();
-// person.address.street = "111 Main St";
-
-// console.log(person.address.street);
-
-// 31) Object and literal
-// var Tony = {
-//     firstName: 'Tony', 
-//     lastName:'Alicea',
-//     address: {
-//         street: '111 Main st.',
-//         city: 'Toronto',
-//         state: 'Ontario'
-//     }
-// };
-
-// function greet(person){
-//     console.log('Hi ' + person.firstName);
-//     console.log('There: ' + person.address.street);
-// }
-
-// greet(Tony);
-
-
diff --git a/lab/js/demo/greet.js b/lab/js/demo/greet.js
deleted file mode 100644
index 1aa1ba3..0000000
--- a/lab/js/demo/greet.js
+++ /dev/null
@@ -1 +0,0 @@
-var greeting = 'Hola';
\ No newline at end of file
diff --git a/lab/js/demo/index.html b/lab/js/demo/index.html
deleted file mode 100644
index d0b4318..0000000
--- a/lab/js/demo/index.html
+++ /dev/null
@@ -1,9 +0,0 @@
-<html>
-    <head>
-
-    </head>
-    <body>
-        <script src="underscore.js"></script>
-        <script src="app.js"></script>
-    </body>
-</html>
\ No newline at end of file
diff --git a/lab/js/demo/underscore.js b/lab/js/demo/underscore.js
deleted file mode 100644
index d5edbf1..0000000
--- a/lab/js/demo/underscore.js
+++ /dev/null
@@ -1,1692 +0,0 @@
-//     Underscore.js 1.9.1
-//     http://underscorejs.org
-//     (c) 2009-2018 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
-//     Underscore may be freely distributed under the MIT license.
-
-(function() {
-
-    // Baseline setup
-    // --------------
-  
-    // Establish the root object, `window` (`self`) in the browser, `global`
-    // on the server, or `this` in some virtual machines. We use `self`
-    // instead of `window` for `WebWorker` support.
-    var root = typeof self == 'object' && self.self === self && self ||
-              typeof global == 'object' && global.global === global && global ||
-              this ||
-              {};
-  
-    // Save the previous value of the `_` variable.
-    var previousUnderscore = root._;
-  
-    // Save bytes in the minified (but not gzipped) version:
-    var ArrayProto = Array.prototype, ObjProto = Object.prototype;
-    var SymbolProto = typeof Symbol !== 'undefined' ? Symbol.prototype : null;
-  
-    // Create quick reference variables for speed access to core prototypes.
-    var push = ArrayProto.push,
-        slice = ArrayProto.slice,
-        toString = ObjProto.toString,
-        hasOwnProperty = ObjProto.hasOwnProperty;
-  
-    // All **ECMAScript 5** native function implementations that we hope to use
-    // are declared here.
-    var nativeIsArray = Array.isArray,
-        nativeKeys = Object.keys,
-        nativeCreate = Object.create;
-  
-    // Naked function reference for surrogate-prototype-swapping.
-    var Ctor = function(){};
-  
-    // Create a safe reference to the Underscore object for use below.
-    var _ = function(obj) {
-      if (obj instanceof _) return obj;
-      if (!(this instanceof _)) return new _(obj);
-      this._wrapped = obj;
-    };
-  
-    // Export the Underscore object for **Node.js**, with
-    // backwards-compatibility for their old module API. If we're in
-    // the browser, add `_` as a global object.
-    // (`nodeType` is checked to ensure that `module`
-    // and `exports` are not HTML elements.)
-    if (typeof exports != 'undefined' && !exports.nodeType) {
-      if (typeof module != 'undefined' && !module.nodeType && module.exports) {
-        exports = module.exports = _;
-      }
-      exports._ = _;
-    } else {
-      root._ = _;
-    }
-  
-    // Current version.
-    _.VERSION = '1.9.1';
-  
-    // Internal function that returns an efficient (for current engines) version
-    // of the passed-in callback, to be repeatedly applied in other Underscore
-    // functions.
-    var optimizeCb = function(func, context, argCount) {
-      if (context === void 0) return func;
-      switch (argCount == null ? 3 : argCount) {
-        case 1: return function(value) {
-          return func.call(context, value);
-        };
-        // The 2-argument case is omitted because we’re not using it.
-        case 3: return function(value, index, collection) {
-          return func.call(context, value, index, collection);
-        };
-        case 4: return function(accumulator, value, index, collection) {
-          return func.call(context, accumulator, value, index, collection);
-        };
-      }
-      return function() {
-        return func.apply(context, arguments);
-      };
-    };
-  
-    var builtinIteratee;
-  
-    // An internal function to generate callbacks that can be applied to each
-    // element in a collection, returning the desired result — either `identity`,
-    // an arbitrary callback, a property matcher, or a property accessor.
-    var cb = function(value, context, argCount) {
-      if (_.iteratee !== builtinIteratee) return _.iteratee(value, context);
-      if (value == null) return _.identity;
-      if (_.isFunction(value)) return optimizeCb(value, context, argCount);
-      if (_.isObject(value) && !_.isArray(value)) return _.matcher(value);
-      return _.property(value);
-    };
-  
-    // External wrapper for our callback generator. Users may customize
-    // `_.iteratee` if they want additional predicate/iteratee shorthand styles.
-    // This abstraction hides the internal-only argCount argument.
-    _.iteratee = builtinIteratee = function(value, context) {
-      return cb(value, context, Infinity);
-    };
-  
-    // Some functions take a variable number of arguments, or a few expected
-    // arguments at the beginning and then a variable number of values to operate
-    // on. This helper accumulates all remaining arguments past the function’s
-    // argument length (or an explicit `startIndex`), into an array that becomes
-    // the last argument. Similar to ES6’s "rest parameter".
-    var restArguments = function(func, startIndex) {
-      startIndex = startIndex == null ? func.length - 1 : +startIndex;
-      return function() {
-        var length = Math.max(arguments.length - startIndex, 0),
-            rest = Array(length),
-            index = 0;
-        for (; index < length; index++) {
-          rest[index] = arguments[index + startIndex];
-        }
-        switch (startIndex) {
-          case 0: return func.call(this, rest);
-          case 1: return func.call(this, arguments[0], rest);
-          case 2: return func.call(this, arguments[0], arguments[1], rest);
-        }
-        var args = Array(startIndex + 1);
-        for (index = 0; index < startIndex; index++) {
-          args[index] = arguments[index];
-        }
-        args[startIndex] = rest;
-        return func.apply(this, args);
-      };
-    };
-  
-    // An internal function for creating a new object that inherits from another.
-    var baseCreate = function(prototype) {
-      if (!_.isObject(prototype)) return {};
-      if (nativeCreate) return nativeCreate(prototype);
-      Ctor.prototype = prototype;
-      var result = new Ctor;
-      Ctor.prototype = null;
-      return result;
-    };
-  
-    var shallowProperty = function(key) {
-      return function(obj) {
-        return obj == null ? void 0 : obj[key];
-      };
-    };
-  
-    var has = function(obj, path) {
-      return obj != null && hasOwnProperty.call(obj, path);
-    }
-  
-    var deepGet = function(obj, path) {
-      var length = path.length;
-      for (var i = 0; i < length; i++) {
-        if (obj == null) return void 0;
-        obj = obj[path[i]];
-      }
-      return length ? obj : void 0;
-    };
-  
-    // Helper for collection methods to determine whether a collection
-    // should be iterated as an array or as an object.
-    // Related: http://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength
-    // Avoids a very nasty iOS 8 JIT bug on ARM-64. #2094
-    var MAX_ARRAY_INDEX = Math.pow(2, 53) - 1;
-    var getLength = shallowProperty('length');
-    var isArrayLike = function(collection) {
-      var length = getLength(collection);
-      return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
-    };
-  
-    // Collection Functions
-    // --------------------
-  
-    // The cornerstone, an `each` implementation, aka `forEach`.
-    // Handles raw objects in addition to array-likes. Treats all
-    // sparse array-likes as if they were dense.
-    _.each = _.forEach = function(obj, iteratee, context) {
-      iteratee = optimizeCb(iteratee, context);
-      var i, length;
-      if (isArrayLike(obj)) {
-        for (i = 0, length = obj.length; i < length; i++) {
-          iteratee(obj[i], i, obj);
-        }
-      } else {
-        var keys = _.keys(obj);
-        for (i = 0, length = keys.length; i < length; i++) {
-          iteratee(obj[keys[i]], keys[i], obj);
-        }
-      }
-      return obj;
-    };
-  
-    // Return the results of applying the iteratee to each element.
-    _.map = _.collect = function(obj, iteratee, context) {
-      iteratee = cb(iteratee, context);
-      var keys = !isArrayLike(obj) && _.keys(obj),
-          length = (keys || obj).length,
-          results = Array(length);
-      for (var index = 0; index < length; index++) {
-        var currentKey = keys ? keys[index] : index;
-        results[index] = iteratee(obj[currentKey], currentKey, obj);
-      }
-      return results;
-    };
-  
-    // Create a reducing function iterating left or right.
-    var createReduce = function(dir) {
-      // Wrap code that reassigns argument variables in a separate function than
-      // the one that accesses `arguments.length` to avoid a perf hit. (#1991)
-      var reducer = function(obj, iteratee, memo, initial) {
-        var keys = !isArrayLike(obj) && _.keys(obj),
-            length = (keys || obj).length,
-            index = dir > 0 ? 0 : length - 1;
-        if (!initial) {
-          memo = obj[keys ? keys[index] : index];
-          index += dir;
-        }
-        for (; index >= 0 && index < length; index += dir) {
-          var currentKey = keys ? keys[index] : index;
-          memo = iteratee(memo, obj[currentKey], currentKey, obj);
-        }
-        return memo;
-      };
-  
-      return function(obj, iteratee, memo, context) {
-        var initial = arguments.length >= 3;
-        return reducer(obj, optimizeCb(iteratee, context, 4), memo, initial);
-      };
-    };
-  
-    // **Reduce** builds up a single result from a list of values, aka `inject`,
-    // or `foldl`.
-    _.reduce = _.foldl = _.inject = createReduce(1);
-  
-    // The right-associative version of reduce, also known as `foldr`.
-    _.reduceRight = _.foldr = createReduce(-1);
-  
-    // Return the first value which passes a truth test. Aliased as `detect`.
-    _.find = _.detect = function(obj, predicate, context) {
-      var keyFinder = isArrayLike(obj) ? _.findIndex : _.findKey;
-      var key = keyFinder(obj, predicate, context);
-      if (key !== void 0 && key !== -1) return obj[key];
-    };
-  
-    // Return all the elements that pass a truth test.
-    // Aliased as `select`.
-    _.filter = _.select = function(obj, predicate, context) {
-      var results = [];
-      predicate = cb(predicate, context);
-      _.each(obj, function(value, index, list) {
-        if (predicate(value, index, list)) results.push(value);
-      });
-      return results;
-    };
-  
-    // Return all the elements for which a truth test fails.
-    _.reject = function(obj, predicate, context) {
-      return _.filter(obj, _.negate(cb(predicate)), context);
-    };
-  
-    // Determine whether all of the elements match a truth test.
-    // Aliased as `all`.
-    _.every = _.all = function(obj, predicate, context) {
-      predicate = cb(predicate, context);
-      var keys = !isArrayLike(obj) && _.keys(obj),
-          length = (keys || obj).length;
-      for (var index = 0; index < length; index++) {
-        var currentKey = keys ? keys[index] : index;
-        if (!predicate(obj[currentKey], currentKey, obj)) return false;
-      }
-      return true;
-    };
-  
-    // Determine if at least one element in the object matches a truth test.
-    // Aliased as `any`.
-    _.some = _.any = function(obj, predicate, context) {
-      predicate = cb(predicate, context);
-      var keys = !isArrayLike(obj) && _.keys(obj),
-          length = (keys || obj).length;
-      for (var index = 0; index < length; index++) {
-        var currentKey = keys ? keys[index] : index;
-        if (predicate(obj[currentKey], currentKey, obj)) return true;
-      }
-      return false;
-    };
-  
-    // Determine if the array or object contains a given item (using `===`).
-    // Aliased as `includes` and `include`.
-    _.contains = _.includes = _.include = function(obj, item, fromIndex, guard) {
-      if (!isArrayLike(obj)) obj = _.values(obj);
-      if (typeof fromIndex != 'number' || guard) fromIndex = 0;
-      return _.indexOf(obj, item, fromIndex) >= 0;
-    };
-  
-    // Invoke a method (with arguments) on every item in a collection.
-    _.invoke = restArguments(function(obj, path, args) {
-      var contextPath, func;
-      if (_.isFunction(path)) {
-        func = path;
-      } else if (_.isArray(path)) {
-        contextPath = path.slice(0, -1);
-        path = path[path.length - 1];
-      }
-      return _.map(obj, function(context) {
-        var method = func;
-        if (!method) {
-          if (contextPath && contextPath.length) {
-            context = deepGet(context, contextPath);
-          }
-          if (context == null) return void 0;
-          method = context[path];
-        }
-        return method == null ? method : method.apply(context, args);
-      });
-    });
-  
-    // Convenience version of a common use case of `map`: fetching a property.
-    _.pluck = function(obj, key) {
-      return _.map(obj, _.property(key));
-    };
-  
-    // Convenience version of a common use case of `filter`: selecting only objects
-    // containing specific `key:value` pairs.
-    _.where = function(obj, attrs) {
-      return _.filter(obj, _.matcher(attrs));
-    };
-  
-    // Convenience version of a common use case of `find`: getting the first object
-    // containing specific `key:value` pairs.
-    _.findWhere = function(obj, attrs) {
-      return _.find(obj, _.matcher(attrs));
-    };
-  
-    // Return the maximum element (or element-based computation).
-    _.max = function(obj, iteratee, context) {
-      var result = -Infinity, lastComputed = -Infinity,
-          value, computed;
-      if (iteratee == null || typeof iteratee == 'number' && typeof obj[0] != 'object' && obj != null) {
-        obj = isArrayLike(obj) ? obj : _.values(obj);
-        for (var i = 0, length = obj.length; i < length; i++) {
-          value = obj[i];
-          if (value != null && value > result) {
-            result = value;
-          }
-        }
-      } else {
-        iteratee = cb(iteratee, context);
-        _.each(obj, function(v, index, list) {
-          computed = iteratee(v, index, list);
-          if (computed > lastComputed || computed === -Infinity && result === -Infinity) {
-            result = v;
-            lastComputed = computed;
-          }
-        });
-      }
-      return result;
-    };
-  
-    // Return the minimum element (or element-based computation).
-    _.min = function(obj, iteratee, context) {
-      var result = Infinity, lastComputed = Infinity,
-          value, computed;
-      if (iteratee == null || typeof iteratee == 'number' && typeof obj[0] != 'object' && obj != null) {
-        obj = isArrayLike(obj) ? obj : _.values(obj);
-        for (var i = 0, length = obj.length; i < length; i++) {
-          value = obj[i];
-          if (value != null && value < result) {
-            result = value;
-          }
-        }
-      } else {
-        iteratee = cb(iteratee, context);
-        _.each(obj, function(v, index, list) {
-          computed = iteratee(v, index, list);
-          if (computed < lastComputed || computed === Infinity && result === Infinity) {
-            result = v;
-            lastComputed = computed;
-          }
-        });
-      }
-      return result;
-    };
-  
-    // Shuffle a collection.
-    _.shuffle = function(obj) {
-      return _.sample(obj, Infinity);
-    };
-  
-    // Sample **n** random values from a collection using the modern version of the
-    // [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher–Yates_shuffle).
-    // If **n** is not specified, returns a single random element.
-    // The internal `guard` argument allows it to work with `map`.
-    _.sample = function(obj, n, guard) {
-      if (n == null || guard) {
-        if (!isArrayLike(obj)) obj = _.values(obj);
-        return obj[_.random(obj.length - 1)];
-      }
-      var sample = isArrayLike(obj) ? _.clone(obj) : _.values(obj);
-      var length = getLength(sample);
-      n = Math.max(Math.min(n, length), 0);
-      var last = length - 1;
-      for (var index = 0; index < n; index++) {
-        var rand = _.random(index, last);
-        var temp = sample[index];
-        sample[index] = sample[rand];
-        sample[rand] = temp;
-      }
-      return sample.slice(0, n);
-    };
-  
-    // Sort the object's values by a criterion produced by an iteratee.
-    _.sortBy = function(obj, iteratee, context) {
-      var index = 0;
-      iteratee = cb(iteratee, context);
-      return _.pluck(_.map(obj, function(value, key, list) {
-        return {
-          value: value,
-          index: index++,
-          criteria: iteratee(value, key, list)
-        };
-      }).sort(function(left, right) {
-        var a = left.criteria;
-        var b = right.criteria;
-        if (a !== b) {
-          if (a > b || a === void 0) return 1;
-          if (a < b || b === void 0) return -1;
-        }
-        return left.index - right.index;
-      }), 'value');
-    };
-  
-    // An internal function used for aggregate "group by" operations.
-    var group = function(behavior, partition) {
-      return function(obj, iteratee, context) {
-        var result = partition ? [[], []] : {};
-        iteratee = cb(iteratee, context);
-        _.each(obj, function(value, index) {
-          var key = iteratee(value, index, obj);
-          behavior(result, value, key);
-        });
-        return result;
-      };
-    };
-  
-    // Groups the object's values by a criterion. Pass either a string attribute
-    // to group by, or a function that returns the criterion.
-    _.groupBy = group(function(result, value, key) {
-      if (has(result, key)) result[key].push(value); else result[key] = [value];
-    });
-  
-    // Indexes the object's values by a criterion, similar to `groupBy`, but for
-    // when you know that your index values will be unique.
-    _.indexBy = group(function(result, value, key) {
-      result[key] = value;
-    });
-  
-    // Counts instances of an object that group by a certain criterion. Pass
-    // either a string attribute to count by, or a function that returns the
-    // criterion.
-    _.countBy = group(function(result, value, key) {
-      if (has(result, key)) result[key]++; else result[key] = 1;
-    });
-  
-    var reStrSymbol = /[^\ud800-\udfff]|[\ud800-\udbff][\udc00-\udfff]|[\ud800-\udfff]/g;
-    // Safely create a real, live array from anything iterable.
-    _.toArray = function(obj) {
-      if (!obj) return [];
-      if (_.isArray(obj)) return slice.call(obj);
-      if (_.isString(obj)) {
-        // Keep surrogate pair characters together
-        return obj.match(reStrSymbol);
-      }
-      if (isArrayLike(obj)) return _.map(obj, _.identity);
-      return _.values(obj);
-    };
-  
-    // Return the number of elements in an object.
-    _.size = function(obj) {
-      if (obj == null) return 0;
-      return isArrayLike(obj) ? obj.length : _.keys(obj).length;
-    };
-  
-    // Split a collection into two arrays: one whose elements all satisfy the given
-    // predicate, and one whose elements all do not satisfy the predicate.
-    _.partition = group(function(result, value, pass) {
-      result[pass ? 0 : 1].push(value);
-    }, true);
-  
-    // Array Functions
-    // ---------------
-  
-    // Get the first element of an array. Passing **n** will return the first N
-    // values in the array. Aliased as `head` and `take`. The **guard** check
-    // allows it to work with `_.map`.
-    _.first = _.head = _.take = function(array, n, guard) {
-      if (array == null || array.length < 1) return n == null ? void 0 : [];
-      if (n == null || guard) return array[0];
-      return _.initial(array, array.length - n);
-    };
-  
-    // Returns everything but the last entry of the array. Especially useful on
-    // the arguments object. Passing **n** will return all the values in
-    // the array, excluding the last N.
-    _.initial = function(array, n, guard) {
-      return slice.call(array, 0, Math.max(0, array.length - (n == null || guard ? 1 : n)));
-    };
-  
-    // Get the last element of an array. Passing **n** will return the last N
-    // values in the array.
-    _.last = function(array, n, guard) {
-      if (array == null || array.length < 1) return n == null ? void 0 : [];
-      if (n == null || guard) return array[array.length - 1];
-      return _.rest(array, Math.max(0, array.length - n));
-    };
-  
-    // Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
-    // Especially useful on the arguments object. Passing an **n** will return
-    // the rest N values in the array.
-    _.rest = _.tail = _.drop = function(array, n, guard) {
-      return slice.call(array, n == null || guard ? 1 : n);
-    };
-  
-    // Trim out all falsy values from an array.
-    _.compact = function(array) {
-      return _.filter(array, Boolean);
-    };
-  
-    // Internal implementation of a recursive `flatten` function.
-    var flatten = function(input, shallow, strict, output) {
-      output = output || [];
-      var idx = output.length;
-      for (var i = 0, length = getLength(input); i < length; i++) {
-        var value = input[i];
-        if (isArrayLike(value) && (_.isArray(value) || _.isArguments(value))) {
-          // Flatten current level of array or arguments object.
-          if (shallow) {
-            var j = 0, len = value.length;
-            while (j < len) output[idx++] = value[j++];
-          } else {
-            flatten(value, shallow, strict, output);
-            idx = output.length;
-          }
-        } else if (!strict) {
-          output[idx++] = value;
-        }
-      }
-      return output;
-    };
-  
-    // Flatten out an array, either recursively (by default), or just one level.
-    _.flatten = function(array, shallow) {
-      return flatten(array, shallow, false);
-    };
-  
-    // Return a version of the array that does not contain the specified value(s).
-    _.without = restArguments(function(array, otherArrays) {
-      return _.difference(array, otherArrays);
-    });
-  
-    // Produce a duplicate-free version of the array. If the array has already
-    // been sorted, you have the option of using a faster algorithm.
-    // The faster algorithm will not work with an iteratee if the iteratee
-    // is not a one-to-one function, so providing an iteratee will disable
-    // the faster algorithm.
-    // Aliased as `unique`.
-    _.uniq = _.unique = function(array, isSorted, iteratee, context) {
-      if (!_.isBoolean(isSorted)) {
-        context = iteratee;
-        iteratee = isSorted;
-        isSorted = false;
-      }
-      if (iteratee != null) iteratee = cb(iteratee, context);
-      var result = [];
-      var seen = [];
-      for (var i = 0, length = getLength(array); i < length; i++) {
-        var value = array[i],
-            computed = iteratee ? iteratee(value, i, array) : value;
-        if (isSorted && !iteratee) {
-          if (!i || seen !== computed) result.push(value);
-          seen = computed;
-        } else if (iteratee) {
-          if (!_.contains(seen, computed)) {
-            seen.push(computed);
-            result.push(value);
-          }
-        } else if (!_.contains(result, value)) {
-          result.push(value);
-        }
-      }
-      return result;
-    };
-  
-    // Produce an array that contains the union: each distinct element from all of
-    // the passed-in arrays.
-    _.union = restArguments(function(arrays) {
-      return _.uniq(flatten(arrays, true, true));
-    });
-  
-    // Produce an array that contains every item shared between all the
-    // passed-in arrays.
-    _.intersection = function(array) {
-      var result = [];
-      var argsLength = arguments.length;
-      for (var i = 0, length = getLength(array); i < length; i++) {
-        var item = array[i];
-        if (_.contains(result, item)) continue;
-        var j;
-        for (j = 1; j < argsLength; j++) {
-          if (!_.contains(arguments[j], item)) break;
-        }
-        if (j === argsLength) result.push(item);
-      }
-      return result;
-    };
-  
-    // Take the difference between one array and a number of other arrays.
-    // Only the elements present in just the first array will remain.
-    _.difference = restArguments(function(array, rest) {
-      rest = flatten(rest, true, true);
-      return _.filter(array, function(value){
-        return !_.contains(rest, value);
-      });
-    });
-  
-    // Complement of _.zip. Unzip accepts an array of arrays and groups
-    // each array's elements on shared indices.
-    _.unzip = function(array) {
-      var length = array && _.max(array, getLength).length || 0;
-      var result = Array(length);
-  
-      for (var index = 0; index < length; index++) {
-        result[index] = _.pluck(array, index);
-      }
-      return result;
-    };
-  
-    // Zip together multiple lists into a single array -- elements that share
-    // an index go together.
-    _.zip = restArguments(_.unzip);
-  
-    // Converts lists into objects. Pass either a single array of `[key, value]`
-    // pairs, or two parallel arrays of the same length -- one of keys, and one of
-    // the corresponding values. Passing by pairs is the reverse of _.pairs.
-    _.object = function(list, values) {
-      var result = {};
-      for (var i = 0, length = getLength(list); i < length; i++) {
-        if (values) {
-          result[list[i]] = values[i];
-        } else {
-          result[list[i][0]] = list[i][1];
-        }
-      }
-      return result;
-    };
-  
-    // Generator function to create the findIndex and findLastIndex functions.
-    var createPredicateIndexFinder = function(dir) {
-      return function(array, predicate, context) {
-        predicate = cb(predicate, context);
-        var length = getLength(array);
-        var index = dir > 0 ? 0 : length - 1;
-        for (; index >= 0 && index < length; index += dir) {
-          if (predicate(array[index], index, array)) return index;
-        }
-        return -1;
-      };
-    };
-  
-    // Returns the first index on an array-like that passes a predicate test.
-    _.findIndex = createPredicateIndexFinder(1);
-    _.findLastIndex = createPredicateIndexFinder(-1);
-  
-    // Use a comparator function to figure out the smallest index at which
-    // an object should be inserted so as to maintain order. Uses binary search.
-    _.sortedIndex = function(array, obj, iteratee, context) {
-      iteratee = cb(iteratee, context, 1);
-      var value = iteratee(obj);
-      var low = 0, high = getLength(array);
-      while (low < high) {
-        var mid = Math.floor((low + high) / 2);
-        if (iteratee(array[mid]) < value) low = mid + 1; else high = mid;
-      }
-      return low;
-    };
-  
-    // Generator function to create the indexOf and lastIndexOf functions.
-    var createIndexFinder = function(dir, predicateFind, sortedIndex) {
-      return function(array, item, idx) {
-        var i = 0, length = getLength(array);
-        if (typeof idx == 'number') {
-          if (dir > 0) {
-            i = idx >= 0 ? idx : Math.max(idx + length, i);
-          } else {
-            length = idx >= 0 ? Math.min(idx + 1, length) : idx + length + 1;
-          }
-        } else if (sortedIndex && idx && length) {
-          idx = sortedIndex(array, item);
-          return array[idx] === item ? idx : -1;
-        }
-        if (item !== item) {
-          idx = predicateFind(slice.call(array, i, length), _.isNaN);
-          return idx >= 0 ? idx + i : -1;
-        }
-        for (idx = dir > 0 ? i : length - 1; idx >= 0 && idx < length; idx += dir) {
-          if (array[idx] === item) return idx;
-        }
-        return -1;
-      };
-    };
-  
-    // Return the position of the first occurrence of an item in an array,
-    // or -1 if the item is not included in the array.
-    // If the array is large and already in sort order, pass `true`
-    // for **isSorted** to use binary search.
-    _.indexOf = createIndexFinder(1, _.findIndex, _.sortedIndex);
-    _.lastIndexOf = createIndexFinder(-1, _.findLastIndex);
-  
-    // Generate an integer Array containing an arithmetic progression. A port of
-    // the native Python `range()` function. See
-    // [the Python documentation](http://docs.python.org/library/functions.html#range).
-    _.range = function(start, stop, step) {
-      if (stop == null) {
-        stop = start || 0;
-        start = 0;
-      }
-      if (!step) {
-        step = stop < start ? -1 : 1;
-      }
-  
-      var length = Math.max(Math.ceil((stop - start) / step), 0);
-      var range = Array(length);
-  
-      for (var idx = 0; idx < length; idx++, start += step) {
-        range[idx] = start;
-      }
-  
-      return range;
-    };
-  
-    // Chunk a single array into multiple arrays, each containing `count` or fewer
-    // items.
-    _.chunk = function(array, count) {
-      if (count == null || count < 1) return [];
-      var result = [];
-      var i = 0, length = array.length;
-      while (i < length) {
-        result.push(slice.call(array, i, i += count));
-      }
-      return result;
-    };
-  
-    // Function (ahem) Functions
-    // ------------------
-  
-    // Determines whether to execute a function as a constructor
-    // or a normal function with the provided arguments.
-    var executeBound = function(sourceFunc, boundFunc, context, callingContext, args) {
-      if (!(callingContext instanceof boundFunc)) return sourceFunc.apply(context, args);
-      var self = baseCreate(sourceFunc.prototype);
-      var result = sourceFunc.apply(self, args);
-      if (_.isObject(result)) return result;
-      return self;
-    };
-  
-    // Create a function bound to a given object (assigning `this`, and arguments,
-    // optionally). Delegates to **ECMAScript 5**'s native `Function.bind` if
-    // available.
-    _.bind = restArguments(function(func, context, args) {
-      if (!_.isFunction(func)) throw new TypeError('Bind must be called on a function');
-      var bound = restArguments(function(callArgs) {
-        return executeBound(func, bound, context, this, args.concat(callArgs));
-      });
-      return bound;
-    });
-  
-    // Partially apply a function by creating a version that has had some of its
-    // arguments pre-filled, without changing its dynamic `this` context. _ acts
-    // as a placeholder by default, allowing any combination of arguments to be
-    // pre-filled. Set `_.partial.placeholder` for a custom placeholder argument.
-    _.partial = restArguments(function(func, boundArgs) {
-      var placeholder = _.partial.placeholder;
-      var bound = function() {
-        var position = 0, length = boundArgs.length;
-        var args = Array(length);
-        for (var i = 0; i < length; i++) {
-          args[i] = boundArgs[i] === placeholder ? arguments[position++] : boundArgs[i];
-        }
-        while (position < arguments.length) args.push(arguments[position++]);
-        return executeBound(func, bound, this, this, args);
-      };
-      return bound;
-    });
-  
-    _.partial.placeholder = _;
-  
-    // Bind a number of an object's methods to that object. Remaining arguments
-    // are the method names to be bound. Useful for ensuring that all callbacks
-    // defined on an object belong to it.
-    _.bindAll = restArguments(function(obj, keys) {
-      keys = flatten(keys, false, false);
-      var index = keys.length;
-      if (index < 1) throw new Error('bindAll must be passed function names');
-      while (index--) {
-        var key = keys[index];
-        obj[key] = _.bind(obj[key], obj);
-      }
-    });
-  
-    // Memoize an expensive function by storing its results.
-    _.memoize = function(func, hasher) {
-      var memoize = function(key) {
-        var cache = memoize.cache;
-        var address = '' + (hasher ? hasher.apply(this, arguments) : key);
-        if (!has(cache, address)) cache[address] = func.apply(this, arguments);
-        return cache[address];
-      };
-      memoize.cache = {};
-      return memoize;
-    };
-  
-    // Delays a function for the given number of milliseconds, and then calls
-    // it with the arguments supplied.
-    _.delay = restArguments(function(func, wait, args) {
-      return setTimeout(function() {
-        return func.apply(null, args);
-      }, wait);
-    });
-  
-    // Defers a function, scheduling it to run after the current call stack has
-    // cleared.
-    _.defer = _.partial(_.delay, _, 1);
-  
-    // Returns a function, that, when invoked, will only be triggered at most once
-    // during a given window of time. Normally, the throttled function will run
-    // as much as it can, without ever going more than once per `wait` duration;
-    // but if you'd like to disable the execution on the leading edge, pass
-    // `{leading: false}`. To disable execution on the trailing edge, ditto.
-    _.throttle = function(func, wait, options) {
-      var timeout, context, args, result;
-      var previous = 0;
-      if (!options) options = {};
-  
-      var later = function() {
-        previous = options.leading === false ? 0 : _.now();
-        timeout = null;
-        result = func.apply(context, args);
-        if (!timeout) context = args = null;
-      };
-  
-      var throttled = function() {
-        var now = _.now();
-        if (!previous && options.leading === false) previous = now;
-        var remaining = wait - (now - previous);
-        context = this;
-        args = arguments;
-        if (remaining <= 0 || remaining > wait) {
-          if (timeout) {
-            clearTimeout(timeout);
-            timeout = null;
-          }
-          previous = now;
-          result = func.apply(context, args);
-          if (!timeout) context = args = null;
-        } else if (!timeout && options.trailing !== false) {
-          timeout = setTimeout(later, remaining);
-        }
-        return result;
-      };
-  
-      throttled.cancel = function() {
-        clearTimeout(timeout);
-        previous = 0;
-        timeout = context = args = null;
-      };
-  
-      return throttled;
-    };
-  
-    // Returns a function, that, as long as it continues to be invoked, will not
-    // be triggered. The function will be called after it stops being called for
-    // N milliseconds. If `immediate` is passed, trigger the function on the
-    // leading edge, instead of the trailing.
-    _.debounce = function(func, wait, immediate) {
-      var timeout, result;
-  
-      var later = function(context, args) {
-        timeout = null;
-        if (args) result = func.apply(context, args);
-      };
-  
-      var debounced = restArguments(function(args) {
-        if (timeout) clearTimeout(timeout);
-        if (immediate) {
-          var callNow = !timeout;
-          timeout = setTimeout(later, wait);
-          if (callNow) result = func.apply(this, args);
-        } else {
-          timeout = _.delay(later, wait, this, args);
-        }
-  
-        return result;
-      });
-  
-      debounced.cancel = function() {
-        clearTimeout(timeout);
-        timeout = null;
-      };
-  
-      return debounced;
-    };
-  
-    // Returns the first function passed as an argument to the second,
-    // allowing you to adjust arguments, run code before and after, and
-    // conditionally execute the original function.
-    _.wrap = function(func, wrapper) {
-      return _.partial(wrapper, func);
-    };
-  
-    // Returns a negated version of the passed-in predicate.
-    _.negate = function(predicate) {
-      return function() {
-        return !predicate.apply(this, arguments);
-      };
-    };
-  
-    // Returns a function that is the composition of a list of functions, each
-    // consuming the return value of the function that follows.
-    _.compose = function() {
-      var args = arguments;
-      var start = args.length - 1;
-      return function() {
-        var i = start;
-        var result = args[start].apply(this, arguments);
-        while (i--) result = args[i].call(this, result);
-        return result;
-      };
-    };
-  
-    // Returns a function that will only be executed on and after the Nth call.
-    _.after = function(times, func) {
-      return function() {
-        if (--times < 1) {
-          return func.apply(this, arguments);
-        }
-      };
-    };
-  
-    // Returns a function that will only be executed up to (but not including) the Nth call.
-    _.before = function(times, func) {
-      var memo;
-      return function() {
-        if (--times > 0) {
-          memo = func.apply(this, arguments);
-        }
-        if (times <= 1) func = null;
-        return memo;
-      };
-    };
-  
-    // Returns a function that will be executed at most one time, no matter how
-    // often you call it. Useful for lazy initialization.
-    _.once = _.partial(_.before, 2);
-  
-    _.restArguments = restArguments;
-  
-    // Object Functions
-    // ----------------
-  
-    // Keys in IE < 9 that won't be iterated by `for key in ...` and thus missed.
-    var hasEnumBug = !{toString: null}.propertyIsEnumerable('toString');
-    var nonEnumerableProps = ['valueOf', 'isPrototypeOf', 'toString',
-      'propertyIsEnumerable', 'hasOwnProperty', 'toLocaleString'];
-  
-    var collectNonEnumProps = function(obj, keys) {
-      var nonEnumIdx = nonEnumerableProps.length;
-      var constructor = obj.constructor;
-      var proto = _.isFunction(constructor) && constructor.prototype || ObjProto;
-  
-      // Constructor is a special case.
-      var prop = 'constructor';
-      if (has(obj, prop) && !_.contains(keys, prop)) keys.push(prop);
-  
-      while (nonEnumIdx--) {
-        prop = nonEnumerableProps[nonEnumIdx];
-        if (prop in obj && obj[prop] !== proto[prop] && !_.contains(keys, prop)) {
-          keys.push(prop);
-        }
-      }
-    };
-  
-    // Retrieve the names of an object's own properties.
-    // Delegates to **ECMAScript 5**'s native `Object.keys`.
-    _.keys = function(obj) {
-      if (!_.isObject(obj)) return [];
-      if (nativeKeys) return nativeKeys(obj);
-      var keys = [];
-      for (var key in obj) if (has(obj, key)) keys.push(key);
-      // Ahem, IE < 9.
-      if (hasEnumBug) collectNonEnumProps(obj, keys);
-      return keys;
-    };
-  
-    // Retrieve all the property names of an object.
-    _.allKeys = function(obj) {
-      if (!_.isObject(obj)) return [];
-      var keys = [];
-      for (var key in obj) keys.push(key);
-      // Ahem, IE < 9.
-      if (hasEnumBug) collectNonEnumProps(obj, keys);
-      return keys;
-    };
-  
-    // Retrieve the values of an object's properties.
-    _.values = function(obj) {
-      var keys = _.keys(obj);
-      var length = keys.length;
-      var values = Array(length);
-      for (var i = 0; i < length; i++) {
-        values[i] = obj[keys[i]];
-      }
-      return values;
-    };
-  
-    // Returns the results of applying the iteratee to each element of the object.
-    // In contrast to _.map it returns an object.
-    _.mapObject = function(obj, iteratee, context) {
-      iteratee = cb(iteratee, context);
-      var keys = _.keys(obj),
-          length = keys.length,
-          results = {};
-      for (var index = 0; index < length; index++) {
-        var currentKey = keys[index];
-        results[currentKey] = iteratee(obj[currentKey], currentKey, obj);
-      }
-      return results;
-    };
-  
-    // Convert an object into a list of `[key, value]` pairs.
-    // The opposite of _.object.
-    _.pairs = function(obj) {
-      var keys = _.keys(obj);
-      var length = keys.length;
-      var pairs = Array(length);
-      for (var i = 0; i < length; i++) {
-        pairs[i] = [keys[i], obj[keys[i]]];
-      }
-      return pairs;
-    };
-  
-    // Invert the keys and values of an object. The values must be serializable.
-    _.invert = function(obj) {
-      var result = {};
-      var keys = _.keys(obj);
-      for (var i = 0, length = keys.length; i < length; i++) {
-        result[obj[keys[i]]] = keys[i];
-      }
-      return result;
-    };
-  
-    // Return a sorted list of the function names available on the object.
-    // Aliased as `methods`.
-    _.functions = _.methods = function(obj) {
-      var names = [];
-      for (var key in obj) {
-        if (_.isFunction(obj[key])) names.push(key);
-      }
-      return names.sort();
-    };
-  
-    // An internal function for creating assigner functions.
-    var createAssigner = function(keysFunc, defaults) {
-      return function(obj) {
-        var length = arguments.length;
-        if (defaults) obj = Object(obj);
-        if (length < 2 || obj == null) return obj;
-        for (var index = 1; index < length; index++) {
-          var source = arguments[index],
-              keys = keysFunc(source),
-              l = keys.length;
-          for (var i = 0; i < l; i++) {
-            var key = keys[i];
-            if (!defaults || obj[key] === void 0) obj[key] = source[key];
-          }
-        }
-        return obj;
-      };
-    };
-  
-    // Extend a given object with all the properties in passed-in object(s).
-    _.extend = createAssigner(_.allKeys);
-  
-    // Assigns a given object with all the own properties in the passed-in object(s).
-    // (https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/assign)
-    _.extendOwn = _.assign = createAssigner(_.keys);
-  
-    // Returns the first key on an object that passes a predicate test.
-    _.findKey = function(obj, predicate, context) {
-      predicate = cb(predicate, context);
-      var keys = _.keys(obj), key;
-      for (var i = 0, length = keys.length; i < length; i++) {
-        key = keys[i];
-        if (predicate(obj[key], key, obj)) return key;
-      }
-    };
-  
-    // Internal pick helper function to determine if `obj` has key `key`.
-    var keyInObj = function(value, key, obj) {
-      return key in obj;
-    };
-  
-    // Return a copy of the object only containing the whitelisted properties.
-    _.pick = restArguments(function(obj, keys) {
-      var result = {}, iteratee = keys[0];
-      if (obj == null) return result;
-      if (_.isFunction(iteratee)) {
-        if (keys.length > 1) iteratee = optimizeCb(iteratee, keys[1]);
-        keys = _.allKeys(obj);
-      } else {
-        iteratee = keyInObj;
-        keys = flatten(keys, false, false);
-        obj = Object(obj);
-      }
-      for (var i = 0, length = keys.length; i < length; i++) {
-        var key = keys[i];
-        var value = obj[key];
-        if (iteratee(value, key, obj)) result[key] = value;
-      }
-      return result;
-    });
-  
-    // Return a copy of the object without the blacklisted properties.
-    _.omit = restArguments(function(obj, keys) {
-      var iteratee = keys[0], context;
-      if (_.isFunction(iteratee)) {
-        iteratee = _.negate(iteratee);
-        if (keys.length > 1) context = keys[1];
-      } else {
-        keys = _.map(flatten(keys, false, false), String);
-        iteratee = function(value, key) {
-          return !_.contains(keys, key);
-        };
-      }
-      return _.pick(obj, iteratee, context);
-    });
-  
-    // Fill in a given object with default properties.
-    _.defaults = createAssigner(_.allKeys, true);
-  
-    // Creates an object that inherits from the given prototype object.
-    // If additional properties are provided then they will be added to the
-    // created object.
-    _.create = function(prototype, props) {
-      var result = baseCreate(prototype);
-      if (props) _.extendOwn(result, props);
-      return result;
-    };
-  
-    // Create a (shallow-cloned) duplicate of an object.
-    _.clone = function(obj) {
-      if (!_.isObject(obj)) return obj;
-      return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
-    };
-  
-    // Invokes interceptor with the obj, and then returns obj.
-    // The primary purpose of this method is to "tap into" a method chain, in
-    // order to perform operations on intermediate results within the chain.
-    _.tap = function(obj, interceptor) {
-      interceptor(obj);
-      return obj;
-    };
-  
-    // Returns whether an object has a given set of `key:value` pairs.
-    _.isMatch = function(object, attrs) {
-      var keys = _.keys(attrs), length = keys.length;
-      if (object == null) return !length;
-      var obj = Object(object);
-      for (var i = 0; i < length; i++) {
-        var key = keys[i];
-        if (attrs[key] !== obj[key] || !(key in obj)) return false;
-      }
-      return true;
-    };
-  
-  
-    // Internal recursive comparison function for `isEqual`.
-    var eq, deepEq;
-    eq = function(a, b, aStack, bStack) {
-      // Identical objects are equal. `0 === -0`, but they aren't identical.
-      // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
-      if (a === b) return a !== 0 || 1 / a === 1 / b;
-      // `null` or `undefined` only equal to itself (strict comparison).
-      if (a == null || b == null) return false;
-      // `NaN`s are equivalent, but non-reflexive.
-      if (a !== a) return b !== b;
-      // Exhaust primitive checks
-      var type = typeof a;
-      if (type !== 'function' && type !== 'object' && typeof b != 'object') return false;
-      return deepEq(a, b, aStack, bStack);
-    };
-  
-    // Internal recursive comparison function for `isEqual`.
-    deepEq = function(a, b, aStack, bStack) {
-      // Unwrap any wrapped objects.
-      if (a instanceof _) a = a._wrapped;
-      if (b instanceof _) b = b._wrapped;
-      // Compare `[[Class]]` names.
-      var className = toString.call(a);
-      if (className !== toString.call(b)) return false;
-      switch (className) {
-        // Strings, numbers, regular expressions, dates, and booleans are compared by value.
-        case '[object RegExp]':
-        // RegExps are coerced to strings for comparison (Note: '' + /a/i === '/a/i')
-        case '[object String]':
-          // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
-          // equivalent to `new String("5")`.
-          return '' + a === '' + b;
-        case '[object Number]':
-          // `NaN`s are equivalent, but non-reflexive.
-          // Object(NaN) is equivalent to NaN.
-          if (+a !== +a) return +b !== +b;
-          // An `egal` comparison is performed for other numeric values.
-          return +a === 0 ? 1 / +a === 1 / b : +a === +b;
-        case '[object Date]':
-        case '[object Boolean]':
-          // Coerce dates and booleans to numeric primitive values. Dates are compared by their
-          // millisecond representations. Note that invalid dates with millisecond representations
-          // of `NaN` are not equivalent.
-          return +a === +b;
-        case '[object Symbol]':
-          return SymbolProto.valueOf.call(a) === SymbolProto.valueOf.call(b);
-      }
-  
-      var areArrays = className === '[object Array]';
-      if (!areArrays) {
-        if (typeof a != 'object' || typeof b != 'object') return false;
-  
-        // Objects with different constructors are not equivalent, but `Object`s or `Array`s
-        // from different frames are.
-        var aCtor = a.constructor, bCtor = b.constructor;
-        if (aCtor !== bCtor && !(_.isFunction(aCtor) && aCtor instanceof aCtor &&
-                                 _.isFunction(bCtor) && bCtor instanceof bCtor)
-                            && ('constructor' in a && 'constructor' in b)) {
-          return false;
-        }
-      }
-      // Assume equality for cyclic structures. The algorithm for detecting cyclic
-      // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
-  
-      // Initializing stack of traversed objects.
-      // It's done here since we only need them for objects and arrays comparison.
-      aStack = aStack || [];
-      bStack = bStack || [];
-      var length = aStack.length;
-      while (length--) {
-        // Linear search. Performance is inversely proportional to the number of
-        // unique nested structures.
-        if (aStack[length] === a) return bStack[length] === b;
-      }
-  
-      // Add the first object to the stack of traversed objects.
-      aStack.push(a);
-      bStack.push(b);
-  
-      // Recursively compare objects and arrays.
-      if (areArrays) {
-        // Compare array lengths to determine if a deep comparison is necessary.
-        length = a.length;
-        if (length !== b.length) return false;
-        // Deep compare the contents, ignoring non-numeric properties.
-        while (length--) {
-          if (!eq(a[length], b[length], aStack, bStack)) return false;
-        }
-      } else {
-        // Deep compare objects.
-        var keys = _.keys(a), key;
-        length = keys.length;
-        // Ensure that both objects contain the same number of properties before comparing deep equality.
-        if (_.keys(b).length !== length) return false;
-        while (length--) {
-          // Deep compare each member
-          key = keys[length];
-          if (!(has(b, key) && eq(a[key], b[key], aStack, bStack))) return false;
-        }
-      }
-      // Remove the first object from the stack of traversed objects.
-      aStack.pop();
-      bStack.pop();
-      return true;
-    };
-  
-    // Perform a deep comparison to check if two objects are equal.
-    _.isEqual = function(a, b) {
-      return eq(a, b);
-    };
-  
-    // Is a given array, string, or object empty?
-    // An "empty" object has no enumerable own-properties.
-    _.isEmpty = function(obj) {
-      if (obj == null) return true;
-      if (isArrayLike(obj) && (_.isArray(obj) || _.isString(obj) || _.isArguments(obj))) return obj.length === 0;
-      return _.keys(obj).length === 0;
-    };
-  
-    // Is a given value a DOM element?
-    _.isElement = function(obj) {
-      return !!(obj && obj.nodeType === 1);
-    };
-  
-    // Is a given value an array?
-    // Delegates to ECMA5's native Array.isArray
-    _.isArray = nativeIsArray || function(obj) {
-      return toString.call(obj) === '[object Array]';
-    };
-  
-    // Is a given variable an object?
-    _.isObject = function(obj) {
-      var type = typeof obj;
-      return type === 'function' || type === 'object' && !!obj;
-    };
-  
-    // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError, isMap, isWeakMap, isSet, isWeakSet.
-    _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp', 'Error', 'Symbol', 'Map', 'WeakMap', 'Set', 'WeakSet'], function(name) {
-      _['is' + name] = function(obj) {
-        return toString.call(obj) === '[object ' + name + ']';
-      };
-    });
-  
-    // Define a fallback version of the method in browsers (ahem, IE < 9), where
-    // there isn't any inspectable "Arguments" type.
-    if (!_.isArguments(arguments)) {
-      _.isArguments = function(obj) {
-        return has(obj, 'callee');
-      };
-    }
-  
-    // Optimize `isFunction` if appropriate. Work around some typeof bugs in old v8,
-    // IE 11 (#1621), Safari 8 (#1929), and PhantomJS (#2236).
-    var nodelist = root.document && root.document.childNodes;
-    if (typeof /./ != 'function' && typeof Int8Array != 'object' && typeof nodelist != 'function') {
-      _.isFunction = function(obj) {
-        return typeof obj == 'function' || false;
-      };
-    }
-  
-    // Is a given object a finite number?
-    _.isFinite = function(obj) {
-      return !_.isSymbol(obj) && isFinite(obj) && !isNaN(parseFloat(obj));
-    };
-  
-    // Is the given value `NaN`?
-    _.isNaN = function(obj) {
-      return _.isNumber(obj) && isNaN(obj);
-    };
-  
-    // Is a given value a boolean?
-    _.isBoolean = function(obj) {
-      return obj === true || obj === false || toString.call(obj) === '[object Boolean]';
-    };
-  
-    // Is a given value equal to null?
-    _.isNull = function(obj) {
-      return obj === null;
-    };
-  
-    // Is a given variable undefined?
-    _.isUndefined = function(obj) {
-      return obj === void 0;
-    };
-  
-    // Shortcut function for checking if an object has a given property directly
-    // on itself (in other words, not on a prototype).
-    _.has = function(obj, path) {
-      if (!_.isArray(path)) {
-        return has(obj, path);
-      }
-      var length = path.length;
-      for (var i = 0; i < length; i++) {
-        var key = path[i];
-        if (obj == null || !hasOwnProperty.call(obj, key)) {
-          return false;
-        }
-        obj = obj[key];
-      }
-      return !!length;
-    };
-  
-    // Utility Functions
-    // -----------------
-  
-    // Run Underscore.js in *noConflict* mode, returning the `_` variable to its
-    // previous owner. Returns a reference to the Underscore object.
-    _.noConflict = function() {
-      root._ = previousUnderscore;
-      return this;
-    };
-  
-    // Keep the identity function around for default iteratees.
-    _.identity = function(value) {
-      return value;
-    };
-  
-    // Predicate-generating functions. Often useful outside of Underscore.
-    _.constant = function(value) {
-      return function() {
-        return value;
-      };
-    };
-  
-    _.noop = function(){};
-  
-    // Creates a function that, when passed an object, will traverse that object’s
-    // properties down the given `path`, specified as an array of keys or indexes.
-    _.property = function(path) {
-      if (!_.isArray(path)) {
-        return shallowProperty(path);
-      }
-      return function(obj) {
-        return deepGet(obj, path);
-      };
-    };
-  
-    // Generates a function for a given object that returns a given property.
-    _.propertyOf = function(obj) {
-      if (obj == null) {
-        return function(){};
-      }
-      return function(path) {
-        return !_.isArray(path) ? obj[path] : deepGet(obj, path);
-      };
-    };
-  
-    // Returns a predicate for checking whether an object has a given set of
-    // `key:value` pairs.
-    _.matcher = _.matches = function(attrs) {
-      attrs = _.extendOwn({}, attrs);
-      return function(obj) {
-        return _.isMatch(obj, attrs);
-      };
-    };
-  
-    // Run a function **n** times.
-    _.times = function(n, iteratee, context) {
-      var accum = Array(Math.max(0, n));
-      iteratee = optimizeCb(iteratee, context, 1);
-      for (var i = 0; i < n; i++) accum[i] = iteratee(i);
-      return accum;
-    };
-  
-    // Return a random integer between min and max (inclusive).
-    _.random = function(min, max) {
-      if (max == null) {
-        max = min;
-        min = 0;
-      }
-      return min + Math.floor(Math.random() * (max - min + 1));
-    };
-  
-    // A (possibly faster) way to get the current timestamp as an integer.
-    _.now = Date.now || function() {
-      return new Date().getTime();
-    };
-  
-    // List of HTML entities for escaping.
-    var escapeMap = {
-      '&': '&amp;',
-      '<': '&lt;',
-      '>': '&gt;',
-      '"': '&quot;',
-      "'": '&#x27;',
-      '`': '&#x60;'
-    };
-    var unescapeMap = _.invert(escapeMap);
-  
-    // Functions for escaping and unescaping strings to/from HTML interpolation.
-    var createEscaper = function(map) {
-      var escaper = function(match) {
-        return map[match];
-      };
-      // Regexes for identifying a key that needs to be escaped.
-      var source = '(?:' + _.keys(map).join('|') + ')';
-      var testRegexp = RegExp(source);
-      var replaceRegexp = RegExp(source, 'g');
-      return function(string) {
-        string = string == null ? '' : '' + string;
-        return testRegexp.test(string) ? string.replace(replaceRegexp, escaper) : string;
-      };
-    };
-    _.escape = createEscaper(escapeMap);
-    _.unescape = createEscaper(unescapeMap);
-  
-    // Traverses the children of `obj` along `path`. If a child is a function, it
-    // is invoked with its parent as context. Returns the value of the final
-    // child, or `fallback` if any child is undefined.
-    _.result = function(obj, path, fallback) {
-      if (!_.isArray(path)) path = [path];
-      var length = path.length;
-      if (!length) {
-        return _.isFunction(fallback) ? fallback.call(obj) : fallback;
-      }
-      for (var i = 0; i < length; i++) {
-        var prop = obj == null ? void 0 : obj[path[i]];
-        if (prop === void 0) {
-          prop = fallback;
-          i = length; // Ensure we don't continue iterating.
-        }
-        obj = _.isFunction(prop) ? prop.call(obj) : prop;
-      }
-      return obj;
-    };
-  
-    // Generate a unique integer id (unique within the entire client session).
-    // Useful for temporary DOM ids.
-    var idCounter = 0;
-    _.uniqueId = function(prefix) {
-      var id = ++idCounter + '';
-      return prefix ? prefix + id : id;
-    };
-  
-    // By default, Underscore uses ERB-style template delimiters, change the
-    // following template settings to use alternative delimiters.
-    _.templateSettings = {
-      evaluate: /<%([\s\S]+?)%>/g,
-      interpolate: /<%=([\s\S]+?)%>/g,
-      escape: /<%-([\s\S]+?)%>/g
-    };
-  
-    // When customizing `templateSettings`, if you don't want to define an
-    // interpolation, evaluation or escaping regex, we need one that is
-    // guaranteed not to match.
-    var noMatch = /(.)^/;
-  
-    // Certain characters need to be escaped so that they can be put into a
-    // string literal.
-    var escapes = {
-      "'": "'",
-      '\\': '\\',
-      '\r': 'r',
-      '\n': 'n',
-      '\u2028': 'u2028',
-      '\u2029': 'u2029'
-    };
-  
-    var escapeRegExp = /\\|'|\r|\n|\u2028|\u2029/g;
-  
-    var escapeChar = function(match) {
-      return '\\' + escapes[match];
-    };
-  
-    // JavaScript micro-templating, similar to John Resig's implementation.
-    // Underscore templating handles arbitrary delimiters, preserves whitespace,
-    // and correctly escapes quotes within interpolated code.
-    // NB: `oldSettings` only exists for backwards compatibility.
-    _.template = function(text, settings, oldSettings) {
-      if (!settings && oldSettings) settings = oldSettings;
-      settings = _.defaults({}, settings, _.templateSettings);
-  
-      // Combine delimiters into one regular expression via alternation.
-      var matcher = RegExp([
-        (settings.escape || noMatch).source,
-        (settings.interpolate || noMatch).source,
-        (settings.evaluate || noMatch).source
-      ].join('|') + '|$', 'g');
-  
-      // Compile the template source, escaping string literals appropriately.
-      var index = 0;
-      var source = "__p+='";
-      text.replace(matcher, function(match, escape, interpolate, evaluate, offset) {
-        source += text.slice(index, offset).replace(escapeRegExp, escapeChar);
-        index = offset + match.length;
-  
-        if (escape) {
-          source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
-        } else if (interpolate) {
-          source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
-        } else if (evaluate) {
-          source += "';\n" + evaluate + "\n__p+='";
-        }
-  
-        // Adobe VMs need the match returned to produce the correct offset.
-        return match;
-      });
-      source += "';\n";
-  
-      // If a variable is not specified, place data values in local scope.
-      if (!settings.variable) source = 'with(obj||{}){\n' + source + '}\n';
-  
-      source = "var __t,__p='',__j=Array.prototype.join," +
-        "print=function(){__p+=__j.call(arguments,'');};\n" +
-        source + 'return __p;\n';
-  
-      var render;
-      try {
-        render = new Function(settings.variable || 'obj', '_', source);
-      } catch (e) {
-        e.source = source;
-        throw e;
-      }
-  
-      var template = function(data) {
-        return render.call(this, data, _);
-      };
-  
-      // Provide the compiled source as a convenience for precompilation.
-      var argument = settings.variable || 'obj';
-      template.source = 'function(' + argument + '){\n' + source + '}';
-  
-      return template;
-    };
-  
-    // Add a "chain" function. Start chaining a wrapped Underscore object.
-    _.chain = function(obj) {
-      var instance = _(obj);
-      instance._chain = true;
-      return instance;
-    };
-  
-    // OOP
-    // ---------------
-    // If Underscore is called as a function, it returns a wrapped object that
-    // can be used OO-style. This wrapper holds altered versions of all the
-    // underscore functions. Wrapped objects may be chained.
-  
-    // Helper function to continue chaining intermediate results.
-    var chainResult = function(instance, obj) {
-      return instance._chain ? _(obj).chain() : obj;
-    };
-  
-    // Add your own custom functions to the Underscore object.
-    _.mixin = function(obj) {
-      _.each(_.functions(obj), function(name) {
-        var func = _[name] = obj[name];
-        _.prototype[name] = function() {
-          var args = [this._wrapped];
-          push.apply(args, arguments);
-          return chainResult(this, func.apply(_, args));
-        };
-      });
-      return _;
-    };
-  
-    // Add all of the Underscore functions to the wrapper object.
-    _.mixin(_);
-  
-    // Add all mutator Array functions to the wrapper.
-    _.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
-      var method = ArrayProto[name];
-      _.prototype[name] = function() {
-        var obj = this._wrapped;
-        method.apply(obj, arguments);
-        if ((name === 'shift' || name === 'splice') && obj.length === 0) delete obj[0];
-        return chainResult(this, obj);
-      };
-    });
-  
-    // Add all accessor Array functions to the wrapper.
-    _.each(['concat', 'join', 'slice'], function(name) {
-      var method = ArrayProto[name];
-      _.prototype[name] = function() {
-        return chainResult(this, method.apply(this._wrapped, arguments));
-      };
-    });
-  
-    // Extracts the result from a wrapped and chained object.
-    _.prototype.value = function() {
-      return this._wrapped;
-    };
-  
-    // Provide unwrapping proxy for some methods used in engine operations
-    // such as arithmetic and JSON stringification.
-    _.prototype.valueOf = _.prototype.toJSON = _.prototype.value;
-  
-    _.prototype.toString = function() {
-      return String(this._wrapped);
-    };
-  
-    // AMD registration happens at the end for compatibility with AMD loaders
-    // that may not enforce next-turn semantics on modules. Even though general
-    // practice for AMD registration is to be anonymous, underscore registers
-    // as a named module because, like jQuery, it is a base library that is
-    // popular enough to be bundled in a third party lib, but not be part of
-    // an AMD load request. Those cases could generate an error when an
-    // anonymous define() is called outside of a loader request.
-    if (typeof define == 'function' && define.amd) {
-      define('underscore', [], function() {
-        return _;
-      });
-    }
-  }());
\ No newline at end of file
diff --git a/lab/js/demo2.js b/lab/js/demo2.js
deleted file mode 100644
index 7e37f82..0000000
--- a/lab/js/demo2.js
+++ /dev/null
@@ -1,8 +0,0 @@
-function test(t) {      //defining a function
-    if (t === undefined) {       //if t=undefined, call tt
-          console.log(t.tt)      //call t
-    }
-    return t;    
-  }
-  var a=10;    //a is a variable with undefined value
-  console.log(test(a)); //function call
\ No newline at end of file
diff --git a/lab/js/demo3.js b/lab/js/demo3.js
deleted file mode 100644
index acbe887..0000000
--- a/lab/js/demo3.js
+++ /dev/null
@@ -1,33 +0,0 @@
-function myFunc(x, y, ...params) { // used rest operator here
-    console.log(x);
-    console.log(y);
-    console.log(params);
-  }
-  
-var inputs = ["a", "b", "c", "d", "e", "f"];
-myFunc(...inputs); 
-
-console.log(x);
-var x = 1;
-//let x=5;
-console.log(x);
-
-// 
-// https://jscomplete.com/learn/lab-functions-scopes/1lx9-var-vs-let
-var x = 5; 
-console.log(x, "\n"); 
-
-// calling y after definition  
-let y = 10; 
-console.log(y, "\n"); 
-
-// calling var z before definition will return undefined 
-console.log(z, "\n"); 
-var z = 2; 
-
-// calling let a before definition will give error 
-let a = 3;
-console.log(a); 
-//let a = 3; 
-
-  // https://dev.to/sagar/three-dots---in-javascript-26ci
\ No newline at end of file
diff --git a/lab/js/demo4.js b/lab/js/demo4.js
deleted file mode 100644
index 4f6b491..0000000
--- a/lab/js/demo4.js
+++ /dev/null
@@ -1,30 +0,0 @@
-// Rest Parameters 
-function myFunc(...[x, y, z]) {
-    return x * y* z;
-  }
-  
-var a = myFunc(1)          // NaN
-var b = myFunc(1, 2)    // 
-var c = myFunc(1, 2, 3)    // 
-var d = myFunc(1, 2, 3, 4) // 6 (fourth parameter is not destructured)
-
-  console.log(a)
-
-  console.log(b)
-
-  console.log(c)
-  console.log(d)
-
-  //Spread Operators
-  console.log('----------------------')
-  var ins = [1, 2, 3, 4]
-  var e = myFunc(...ins)
-  console.log(e)
-
-
-  const featured = ['Deep Dish', 'Pepperoni', 'Hawaiian'];
-const specialty = ['Meatzza', 'Spicy Mama', 'Margherita'];
-
-const pizzas = [...featured, 'veg pizza', ...specialty];
-
-console.log(pizzas);
diff --git a/lab/js/demo5.js b/lab/js/demo5.js
deleted file mode 100644
index 54514df..0000000
--- a/lab/js/demo5.js
+++ /dev/null
@@ -1,69 +0,0 @@
-
-
-// function hoist() {
-//     a = 20;
-//     var b = 100;
-//     c = a + b;
-//     console.log('hoist fn:' + c );
-//   }
-
-// hoist();
-
-// console.log(a);
-// // console.log(b);
-// console.log(c);
-// 'use strict';
-
-// hoisted(); 
-
-// var hoisted = function hoist() {
-//     console.log('This function has been hoisted.');
-//   };
-
-// function greet(whatso) {
-//   return function(name){
-//     console.log(whatso + ':' + name);
-//   }
-// }
-
-// // greet('Hi')('Tony');
-
-// const greet2 = greet('Hi');
-// greet2('Tom');
-
-// Closure !!
-function createCounter() {
-  let counter = 1
-  const myFunction = function() {
-    counter = counter + 1
-    return counter
-  }
-  return myFunction
-}
-const increment = createCounter()
-const c1 = increment()
-const c2 = increment()
-const c3 = increment()
-console.log('example increment', c1, c2, c3)
- 
- 
-
-
-// const EventEmitter = require('events');
-
-// class MyEmitter extends EventEmitter {}
-
-// const myEmitter = new MyEmitter();
-// myEmitter.on('event', () => {
-//   console.log('an event occurred!');
-// });
-// myEmitter.emit('event');
-
-
-// Node : question
-/*** 
- * 
-https://www.fullstack.cafe/blog/7-hardest-nodejs-interview-questions-and-answers
-
-* 
-*/
diff --git a/lab/js/demo6.js b/lab/js/demo6.js
deleted file mode 100644
index 386bbcb..0000000
--- a/lab/js/demo6.js
+++ /dev/null
@@ -1,5 +0,0 @@
-
-var tools = require('./data.js');
-var value = tools.sum(10,20);
-console.log("Value: "+value);
-tools.ping();
\ No newline at end of file
diff --git a/lab/js/demo7.js b/lab/js/demo7.js
deleted file mode 100644
index 3f3022c..0000000
--- a/lab/js/demo7.js
+++ /dev/null
@@ -1,11 +0,0 @@
-
-let map = new Map();
-
-let john = { name: "John" };
-
-let visitsCountMap = new Map();
-
-// john is the key for the map
-visitsCountMap.set(john, 123);
-
-console.log( visitsCountMap.get(john) ); // 123
\ No newline at end of file
diff --git a/lab/js/demo71.js b/lab/js/demo71.js
deleted file mode 100644
index 9cab82c..0000000
--- a/lab/js/demo71.js
+++ /dev/null
@@ -1,46 +0,0 @@
-
-let name1 = "john";
-
-let john = {
-    cnt1: 0,
-    cnt2: 0,
-    cnt3: 0
-};
-
-let name2 = "simon";
-
-let simon = {
-    cnt1: 0,
-    cnt2: 0,
-    cnt3: 0
-};
-
-let endpointsMap = new Map();
-
-// john is the key for the map
-endpointsMap.set(name1, john);
-endpointsMap.set(name2, simon);
-
-const v1 = endpointsMap.get(name1);
-const v2 = endpointsMap.get(name2);
-// console.log("v=" + v1);
-
-// for (let endpoint of endpointsMap.keys()) {
-//     console.log(endpoint); // 
-// }
-
-endpointsMap.forEach((value, key) => {
-    console.log(key, value);
-});
-
-simon.cnt1++;
-john.cnt3++;
-
-endpointsMap.forEach((value, key) => {
-    console.log(key, value);
-});
-
-john.cnt3++;
-endpointsMap.forEach((value, key) => {
-    console.log(key, value);
-});
diff --git a/lab/js/hackerrank.js b/lab/js/hackerrank.js
deleted file mode 100644
index 1723ed5..0000000
--- a/lab/js/hackerrank.js
+++ /dev/null
@@ -1,39 +0,0 @@
-process.stdin.setEncoding('utf-8');
-
-let inputString = '';
-let currentLine = 0;
-
-process.stdin.on('data', inputStdin => {
-    inputString += inputStdin;
-});
-
-process.stdin.on('end', _ => {
-    inputString = inputString.trim().split('\n').map(string => {
-        return string.trim();
-    });
-    
-    main();    
-});
-
-function readLine() {
-    return inputString[currentLine++];
-}
-
-
-function greeting(parameterVariable) {
-    // This line prints 'Hello, World!' to the console:
-    console.log('Hello, World!');
-
-    // Write a line of code that prints parameterVariable to stdout using console.log:
-    console.log(parameterVariable);
-
-}
-
-
-function main() {
-    const parameterVariable = readLine();
-    
-    greeting(parameterVariable);
-}
-
-main();
\ No newline at end of file
diff --git a/lab/js/main.js b/lab/js/main.js
deleted file mode 100644
index b9ed154..0000000
--- a/lab/js/main.js
+++ /dev/null
@@ -1,4 +0,0 @@
-// import {sayHi, sayBye} from './say.js';
-const sayHi = require("say");
-sayHi('John');  // Hello, John!
-sayBye('John'); // Bye, John!
\ No newline at end of file
diff --git a/lab/js/run.js b/lab/js/run.js
deleted file mode 100644
index 9fe855f..0000000
--- a/lab/js/run.js
+++ /dev/null
@@ -1,25 +0,0 @@
-
-let hdxFile = new Set(['A','B','C','D']);
-let hdxDynamo = new Set(['A','B','X','C']);
-
-let diffMinus = new Set([...hdxDynamo].filter(i => !hdxFile.has(i)));
-let diffPlus = new Set([...hdxFile].filter(i => !hdxDynamo.has(i)));
-console.log(diffMinus);
-console.log(diffPlus);
-
-// let a = new Set([1,2,3]);
-// let b = new Set([4,3,2]);
-// let difference = new Set([...a].filter(x => !b.has(x)));
-// console.log(difference);
-
-/**
- * https://github.com/psean21c/monk/tree/master/src/com/leetcode
- * 
- * LeetCode 525 (week20) 
- * https://github.com/psean21c/monk/blob/master/resource/java/algo/minmax/ContiguousArray.md
- * 
- * https://github.com/psean21c/AlgorithmLib/tree/master/useMax
- * 
- * Whiteboard animation 
- * https://www.youtube.com/watch?v=ft8IPX6RXuo
- */
\ No newline at end of file
diff --git a/lab/js/say.js b/lab/js/say.js
deleted file mode 100644
index 207f02b..0000000
--- a/lab/js/say.js
+++ /dev/null
@@ -1,21 +0,0 @@
-
-function sayHi(user) {
-    alert(`Hello, ${user}!`);
-}
-
-function sayBye(user) {
-    alert(`Bye, ${user}!`);
-}
-
-
-
-export { sayHi, sayBye }; // a list of exported variables
-// const issue1 = function issueReward(){
-//     console.log('run issueReward');
-// }
-
-// export default {issue1};
-
-// export default function cube(x) {
-//     return x * x * x;
-// }
diff --git a/lab/leetcode/find.js b/lab/leetcode/find.js
deleted file mode 100644
index 139597f..0000000
--- a/lab/leetcode/find.js
+++ /dev/null
@@ -1,2 +0,0 @@
-
-
diff --git a/lab/leetcode/tic.js b/lab/leetcode/tic.js
deleted file mode 100644
index a2d35df..0000000
--- a/lab/leetcode/tic.js
+++ /dev/null
@@ -1,114 +0,0 @@
-/**
- * Initialize your data structure here.
- * @param {number} n
- * 
- * Design a Tic-tac-toe game that is played between two players on a n x n grid.
- * 
- * You may assume the following rules:
- * 1) A move is guaranteed to be valid and is placed on an empty block.
- * 2) Once a winning condition is reached, no more moves is allowed.
- * 3) A player who succeeds in placing n of their marks in a horizontal, vertical, or diagonal row wins the game.
- */
-
-var TicTacToe = function(n) {
-    
-};
-
-/**
- * Player {player} makes a move at ({row}, {col}).
-        @param row The row of the board.
-        @param col The column of the board.
-        @param player The player, can be either 1 or 2.
-        @return The current winning condition, can be either:
-                0: No one wins.
-                1: Player 1 wins.
-                2: Player 2 wins. 
- * @param {number} row 
- * @param {number} col 
- * @param {number} player
- * @return {number}
- */
-TicTacToe.prototype.move = function(row, col, player) {
-    console.log(row, ":", col, ":",player);
-};
-
-const n = 1;
-let row=0, col=0, player=0;
-var obj = new TicTacToe(n);
-var param_1 = obj.move(row,col,player);
-
-var abc = function(a,b) {
-    let c = ab;
-    console.log(c);
-}
-let a = 2, b=3;
-abc(a,b);
-
-/** 
- * Your TicTacToe object will be instantiated and called as such:
- * var obj = new TicTacToe(n)
- * var param_1 = obj.move(row,col,player)
- */
-
-/**
- * 
-Given n = 3, assume that player 1 is "X" and player 2 is "O" in the board.
-
-TicTacToe toe = new TicTacToe(3);
-
-toe.move(0, 0, 1); -> Returns 0 (no one wins)
-|X| | |
-| | | |    // Player 1 makes a move at (0, 0).
-| | | |
-
-toe.move(0, 2, 2); -> Returns 0 (no one wins)
-|X| |O|
-| | | |    // Player 2 makes a move at (0, 2).
-| | | |
-
-toe.move(2, 2, 1); -> Returns 0 (no one wins)
-|X| |O|
-| | | |    // Player 1 makes a move at (2, 2).
-| | |X|
-
-toe.move(1, 1, 2); -> Returns 0 (no one wins)
-|X| |O|
-| |O| |    // Player 2 makes a move at (1, 1).
-| | |X|
-
-toe.move(2, 0, 1); -> Returns 0 (no one wins)
-|X| |O|
-| |O| |    // Player 1 makes a move at (2, 0).
-|X| |X|
-
-toe.move(1, 0, 2); -> Returns 0 (no one wins)
-|X| |O|
-|O|O| |    // Player 2 makes a move at (1, 0).
-|X| |X|
-
-toe.move(2, 1, 1); -> Returns 1 (player 1 wins)
-|X| |O|
-|O|O| |    // Player 1 makes a move at (2, 1).
-|X|X|X|
-
-
-["TicTacToe","move","move","move","move","move","move","move"]
-[[3],[0,0,1],[0,2,2],[2,2,1],[1,1,2],[2,0,1],[1,0,2],[2,1,1]]
-
-
- */
-
-class formatDate extends Date {
-    constructor(dateStr) {
-      super(dateStr);
-    }
-  
-    getFormattedDate() {
-      var months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
-                    'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
-  
-      return `${this.getDate()}-${months[this.getMonth()]}-${this.getFullYear()}`;
-    }
-  }
-  
-  console.log(new formatDate('August 19, 1975 23:15:30').getFormattedDate());
\ No newline at end of file
diff --git a/lab/note.txt b/lab/note.txt
index 9bc3229..84ccaab 100644
--- a/lab/note.txt
+++ b/lab/note.txt
@@ -1,11 +1,21 @@
-/** List of library 
+
+/***************************************************************************
+** Basic syntax for npm in order to install npm package
+** When you start a new project with existing package.json,
+** you need to run 'npm init' or remove package-lock.json 
+** before running 'npm install'
 ***************************************************************************/
-npm install --save-dev nodemon // need for auto-refresh
-npm install express --save // web server
-npm install morgan // print log in the console
+$ npm install express --save // web server
+
+$ npm install nodemon  // need for auto-refresh
+                       // Also,usually need an option --save-dev because it's usage
+$ npm prune            // remove modules not specified in the package.json file
 
-/** How to use morgan 
+/***************************************************************************
+** How to use morgan 
 ***************************************************************************/
+$ npm install morgan // print log in the console
+
 var express = require('express'),
   app = express(),
   port = process.env.PORT || 3000;
@@ -18,13 +28,15 @@ app.listen(port, () => {
     console.log('todo list RESTful API server started on: ' + port);
 });
 
-/** How to use nodemon 
+/***************************************************************************
+** How to use nodemon 
 ***************************************************************************/
 - Don't need to import, Just run it in the command line
 $ nodemon .\server2.js // use nodemon instead of node
 
 
-/** Login + Registration with Passport 
+/***************************************************************************
+** Login + Registration with Passport 
 ***************************************************************************/
 
 https://www.youtube.com/watch?v=IlpU1z3cvSQ&index=4&list=PLwbqtYnbSiYLqKQVaq70f-OG70Y2UslqN
diff --git a/package.json b/package.json
index a96d147..fe7dbe8 100644
--- a/package.json
+++ b/package.json
@@ -1,29 +1,39 @@
 {
-  "name": "pod1",
+  "name": "app-connect",
   "version": "1.0.0",
-  "description": "",
-  "main": "one.js",
+  "description": "## Dec-10(Tue), 2019 ThemeForest   - Metronic  - Fuse",
+  "main": "server.js",
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "start": "node server.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/psean21c/App-Connect.git"
   },
   "author": "",
   "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/psean21c/App-Connect/issues"
+  },
+  "homepage": "https://github.com/psean21c/App-Connect#readme",
   "dependencies": {
-    "body-parser": "^1.18.3",
+    "body-parser": "^1.19.0",
     "cors": "^2.8.5",
-    "errorhandler": "^1.5.0",
-    "express": "^4.16.4",
-    "express-session": "^1.15.6",
-    "mongoose": "^5.3.14",
-    "morgan": "^1.9.1",
-    "mysql": "^2.16.0",
-    "passport": "^0.4.0",
+    "crypto": "^1.0.1",
+    "errorhandler": "^1.5.1",
+    "express": "^4.17.1",
+    "express-session": "^1.17.1",
+    "mongoose": "^5.12.6",
+    "morgan": "^1.10.0",
+    "node-fetch": "^2.6.1",
+    "passport": "^0.4.1",
     "passport-http-bearer": "^1.0.1",
-    "pg": "^7.6.0",
-    "request": "^2.88.0",
-    "swagger-ui-express": "^4.0.1"
+    "pg": "^8.6.0",
+    "request": "^2.88.2"
   },
   "devDependencies": {
-    "nodemon": "^1.18.5"
+    "chai": "^4.3.4",
+    "nodemon": "^2.0.7"
   }
 }