promise-imp

js-advanced/implement/promise/index.js

@@ -0,0 +1,66 @@
+const Pedding = 'pedding'
+const Resolved = 'resolved'
+const Rejected = 'rejected'
+
+class MyPromise {
+    constructor(executor) {
+
+        this.status = Pedding;
+
+
+        const resolve = (data) => {
+            this.status = Resolved
+            this.data = data;
+            return this;
+        }
+
+        const reject = (data) => {
+            this.status = Rejected
+            this.data = data;
+            return this;
+        }
+
+        executor(resolve, reject)
+    }
+
+    then(onFulfilled, onRejected) {
+        onFulfilled = isFunction(onFulfilled)? onFulfilled: (value) => value;
+        onRejected = isFunction(onRejected)? onRejected: (value) => {
+            throw err;
+        };
+
+        return new MyPromise((resolve, reject) => {
+            if(this.status === Resolved) {
+                onFulfilled(this.data);
+            }else if(this.status === Rejected) {
+                onRejected
+            }
+        })
+    }
+
+    catch() {
+
+    }
+
+    finally() {
+
+    }
+}
+
+function isFunction(fn) {
+    return fn instanceof Function;
+}
+
+
+const  abc = new Promise((resolve,reject) => {
+    resolve(1)
+})
+
+
+abc.then((data) => {
+    console.log(data);
+})
+
+
+
+

js-advanced/implement/promise/test.js

@@ -0,0 +1,17 @@
+Promise.resolve('good').then((data) => {
+    console.log(data)
+}).then(rst => {
+    console.log(rst);
+})
+
+Promise.reject('err').then((data) => {
+    console.log(data)
+},(err) => {
+    console.log('err: ', err)
+})
+
+new Promise((resolve, reject) => {
+    resolve(1);
+}).then(data => {
+    console.log(data);
+})