From bece99e08f7492e570cd2f837bd57a9c9773b922 Mon Sep 17 00:00:00 2001
From: Zeshi Zheng <mailtozeshi@gmail.com>
Date: Tue, 26 Mar 2019 18:55:43 -0400
Subject: [PATCH] implement simple observer pattern/publisher-subscriber
 pattern

---
 Observable.js | 13 ++++++++-----
 PubSub.js     | 10 ++++++----
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/Observable.js b/Observable.js
index 03545cd..0636125 100644
--- a/Observable.js
+++ b/Observable.js
@@ -10,13 +10,14 @@ class ObserverList {
     this.observerList = [];
   }
   add(observer) {
-    // todo add observer to list
+      this.observerList.push(observer);
   }
   remove(observer) {
-    // todo remove observer from list
+	  this.observerList = this.observerList.filter(item => item !== observer);
   }
   count() {
     // return observer list size
+      return this.observerList.length;
   }
 }
 
@@ -25,13 +26,15 @@ class Subject {
     this.observers = new ObserverList();
   }
   addObserver(observer) {
-    // todo add observer
+      this.observers.add(observer);
   }
   removeObserver(observer) {
-    // todo remove observer
+      this.observers.remove(observer);
   }
   notify(...args) {
-    // todo notify
+      this.observers.observerList.forEach(item => {
+        item.update(...args);
+      })
   }
 }
 
diff --git a/PubSub.js b/PubSub.js
index 0c7999e..3dcdc08 100644
--- a/PubSub.js
+++ b/PubSub.js
@@ -12,15 +12,17 @@ module.exports = class PubSub {
   }
 
   subscribe(type, fn) {
-    // todo subscribe
+      this.subscribers[type] = fn;
   }
 
   unsubscribe(type, fn) {
-    // todo unsubscribe
+      this.subscribers[type] = null;
   }
 
   publish(type, ...args) {
-    // todo publish
+      if (this.subscribers[type]) {
+        this.subscribers[type].call(this, ...args);
+      }
   }
 
-}
+};