标准网站建设价格,个人网页设计手绘,单位网站建设典型材料,自适应网站建设公司目录
1.概念
2.本质
3.语法
4.特点
5.async基本使用
6.async里的await普通函数返回值
7.async里的await Promise函数成功返回值 8.async里的await Promise函数失败返回值 9.解决async里的await Promise函数失败后不执行下面内容 1.概念 真正意义上解决异步回调的问题同步流程表达异步操作 2.本质 Generator的语法糖 3.语法
async function foo(){await 异步操作;await 异步操作;
}
4.特点 1、不需要像Generator去调用next 方法遇到await等待当前的异步操作完成就往下执行 2、返回的点是promise对象可以用then 万法进行下一步操作 3、async取代Generator西数的星号*await取Generator的yield 4、语意上更为明确使用简单 5.async基本使用
!DOCTYPE html
html langen
headmeta charsetUTF-8titleTitle/title
/head
body
script typetext/javascript srchttps://code.jquery.com/jquery-1.10.1.min.js/script
script typetext/javascript// async 基本用法async function foo(){return new Promise(resolve {setTimeout(resolve,2000)})}async function testAsync(){console.log(开始执行,new Date().toTimeString())await foo();console.log(开始执行,new Date().toTimeString())}testAsync();/script
/body
/html
6.async里的await普通函数返回值
!DOCTYPE html
html langen
headmeta charsetUTF-8titleasync/title
/head
body
script typetext/javascript srchttps://code.jquery.com/jquery-1.10.1.min.js/script
script typetext/javascriptfunction test2(){return {code:200,data:{}}}// async 里面 await 返回值async function asyncPrint(){let res await test2();console.log(res)}asyncPrint()
/script
/body
/html 7.async里的await Promise函数成功返回值
!DOCTYPE html
html langen
headmeta charsetUTF-8titleasync/title
/head
body
script typetext/javascript srchttps://code.jquery.com/jquery-1.10.1.min.js/script
script typetext/javascript// async 里面 await 返回值async function asyncPrint(){let res await Promise.resolve({key:value});console.log(res)}asyncPrint()
/script
/body
/html 8.async里的await Promise函数失败返回值 解决报错后面代码不执行 !DOCTYPE html
html langen
headmeta charsetUTF-8titleasync/title
/head
body
script typetext/javascript srchttps://code.jquery.com/jquery-1.10.1.min.js/script
script typetext/javascript// async 里面 await 返回值async function asyncPrint(){let res await Promise.reject({code:400});console.log(res)}asyncPrint()
/script
/body
/html 9.解决async里的await Promise函数失败后不执行下面内容
!DOCTYPE html
html langen
headmeta charsetUTF-8titleasync/title
/head
body
script typetext/javascript srchttps://code.jquery.com/jquery-1.10.1.min.js/script
script typetext/javascriptasync function test(obj){return new Promise((resolve,reject){// 模拟异常// key1为异常异常处理也用resolve()函数if(obj.key1){resolve(false);}else{resolve({code:200})}})}// async 里面 await 返回值async function asyncPrint(){let res await test({key:1});console.log(res)console.log(12313)}asyncPrint()/script
/body
/html
