1.async 函数声明及调用方式：

1 // async 函数声明,调用 2 const a1 = async() => { 3     console.log("this is an async function1") 4 }; 5  6 async function a2() { 7     console.log("this is an async function2") 8 } 9 10 a1();11 a2();12 ;(async ()=>{console.log("this is an async function3")})()

 

2.async 函数返回值：async 函数会返回一个Promise对象，所以处理返回值的方式和Promise一毛一样

1 // async 函数返回值2 const b1 = async (arg) => {3     return arg4 }5 var res = b1('hello');6 res.then(resolve=>{console.log(resolve)});

 

3.直接获取async 函数返回值： await

1 // 直接获取 async函数返回值: await需要与 async 函数搭配2 var ret = async (x) => {3     return x4 }5 var solve = async () => {6     var some_ret = await ret('hello,world');7     console.log(some_ret);8 }9 solve();

1 // 也可以直接获取 Promise 返回值2 var solvePromise = async() => {3     var some_ret = await new Promise(resolve=>{4         resolve('hello, world')5     })6     console.log(some_ret);7 }8 solvePromise();

await的作用是 中断当前函数体中语句的执行, 等待await 后 Promise 执行完毕;

4.async 函数串行执行

1 // async 函数串行执行方式2 const a = async() => {3     const b = await (async () => {})()4     const c = await (async () => {})()5 }6 a();

 

5.async 函数并行执行

1 // async 函数并行执行方式2 const a = async () => {3     const b = (async () => {})()4     const c = (async () => {})()5     const b1 = await b;6     const c1 = await c;7 }8 a();9 // b,c 会分别先执行, 在b1 和 c1 变成串行