From f0837dbfdfc2e677928d67b4fbc0410d3f79f126 Mon Sep 17 00:00:00 2001
From: kangkai <kangk26@foxmail.com>
Date: Wed, 07 Apr 2021 19:49:09 +0800
Subject: [PATCH] Promise约定与链式调用
---
Promise.html | 40 ++++++++++++++++++++++++++++------------
1 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/Promise.html b/Promise.html
index 43a81cc..a8fe8fe 100644
--- a/Promise.html
+++ b/Promise.html
@@ -11,28 +11,44 @@
};
function successCallBack1(){
console.log("成功1");
+ return new Promise((resolve,reject) => {
+ reject();
+ })
};
function failureCallBack1(){
console.log("失败1");
};
+ function successCallBack2(){
+ console.log("成功2");
+ };
+ function failureCallBack2(){
+ console.log("失败2");
+ };
const wait = ()=> new Promise((resolve,reject)=> {
setTimeout(() => {
- console.log('setTimeout1执行完毕');
+ console.log('setTimeout执行完毕');
resolve();
}, 0);
- });
-
- //调用报错，wait2返回的是setTimeout方法。
- const wait1 = ()=> setTimeout(() => {
- console.log('setTimeout2执行完毕');
- return new Promise((resolve,reject)=> {
- resolve();
- });
- }, 0);
+ });
+
+ const wait2 = ()=> new Promise((resolve,reject)=> {
+ resolve();
+ setTimeout(() => {
+ console.log('setTimeout执行完毕');
+ }, 1000);
+ });
-
- var use = wait().then(successCallBack,failureCallBack).then(successCallBack1,failureCallBack1);
+ //Promise约定与链式调用
+ //1.在本轮 事件循环 运行完成之前，回调函数是不会被调用的。以下是个错误示例，resolve回调方法要在setTimeout执行完后在调用。
+ var use = wait2().then(successCallBack,failureCallBack);
+ //2.即使异步操作已经完成（成功或失败），在这之后通过 then() 添加的回调函数也会被调用。
+ var use2 = wait();
+ setTimeout(() => {
+ use.then(successCallBack,failureCallBack);
+ }, 2000);
+ //3.通过多次调用 then() 可以添加多个回调函数，它们会按照插入顺序进行执行。一般情况下then会返回一个默认的Promise对象。
+ var use3 = wait().then(successCallBack,failureCallBack).then(successCallBack1,failureCallBack1).then(successCallBack2,failureCallBack2);
</script>
</head>
<body>
--
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