From 5cf134cdc40a58bd50abfd9149fada82a30821af Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=A9=B9=E7=A9=8E?=
 <5431277+zhanying189@user.noreply.gitee.com>
Date: Mon, 24 May 2021 15:07:59 +0800
Subject: [PATCH] update part1/fed-e-task-01-01/code/MyPromise.js.

---
 part1/fed-e-task-01-01/code/MyPromise.js | 51 +++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/part1/fed-e-task-01-01/code/MyPromise.js b/part1/fed-e-task-01-01/code/MyPromise.js
index 1a6b829..be90ff6 100644
--- a/part1/fed-e-task-01-01/code/MyPromise.js
+++ b/part1/fed-e-task-01-01/code/MyPromise.js
@@ -1,3 +1,52 @@
 /*
 尽可能还原 Promise 中的每一个 API, 并通过注释的方式描述思路和原理.
-*/
\ No newline at end of file
+*/
+const PENDING='pending';
+const RESOLVED='resolved';
+const REJECTED='rejected';//三种状态
+
+function MyPromise(fn){//接收一个函数，会立即执行
+    const that=this;
+    this.state=PENDING;//promise的初始状态
+    this.value=null;//value用于保存resolve 或reject中传入的值
+
+    that.resolvedCallbacks=[];//用于保存then中的回调
+    that.rejectedCallbacks=[];
+
+    function resolve(value){
+        if(that.state===PENDING){//判断当前状态是否pending
+            that.state=RESOLVED;
+            that.value=value;     
+            that.resolvedCallbacks.map(cb=>cb(that.value))//遍历回调数组并且执行
+        }
+    }
+    function reject(value){
+        if(that.state===PENDING){
+            that.state=REJECTED;
+            that.value=value;     
+            that.rejectedCallbacks.map(cb=>cb(that.value))
+        }
+    }
+    try{
+        fn(resolve,reject)
+    }catch(e){
+        reject(e)
+    }
+}
+MyPromise.prototype.then=function(onFullfilled,onRejected){
+    const that=this;
+
+    onFullfilled=typeof onFullfilled === 'function' ? onFullfilled:v=>v
+    onRejected=typeof onRejected === 'function' ? onRejected:e=>throw e
+
+    if(this.state===PENDING){
+        this.resolvedCallbacks.push(onFullfilled)
+        this.rejectedCallbacks.push(onRejected)
+    }
+    if(this.state===PENDING){
+        onFullfilled(that.value)
+    }
+    if(this.state===REJECTED){
+        onRejected(that.value)
+    }
+}
\ No newline at end of file
-- 
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