async await wait()
时间: 2023-11-14 19:09:31 浏览: 123
async/await 是 ES2017 中引入的一种异步编程的语法糖,它可以让我们更方便地编写异步代码。async/await 的本质是 Promise,它可以让我们用同步的方式编写异步代码,使得代码更加易读易懂。
async/await 的用法如下:
async function foo() {
const result = await someAsyncFunction();
console.log(result);
}
其中,async 表示这是一个异步函数,函数内部可以使用 await 关键字等待一个 Promise 对象的结果。当 await 关键字后面的 Promise 对象 resolve 时,await 表达式的值就是 resolve 的结果。
相关问题
async await
Async/await is a feature in modern JavaScript that allows developers to write asynchronous code in a synchronous style. The async keyword is used to define a function that returns a promise, while the await keyword is used to wait for the resolution of a promise.
Async/await is a more readable and easier-to-understand way to write asynchronous code than using callbacks or promises. It allows developers to write code that looks like regular synchronous code, making it easier to reason about and debug.
Here's an example of using async/await to fetch data from an API:
```
async function fetchData() {
const response = await fetch('https://jsonplaceholder.typicode.com/todos/1');
const data = await response.json();
console.log(data);
}
fetchData();
```
In this example, the fetchData function is declared as async and returns a promise. Inside the function, we use the await keyword to wait for the fetch request to complete and the response to be returned. Once we have the response, we use another await keyword to wait for the response to be parsed as JSON. Finally, we log the data to the console.
Async/await is a powerful tool for writing asynchronous code and is widely used in modern JavaScript applications.
async await ES6
ES6中的async和await是用于处理异步操作的关键字。async关键字用于声明一个函数是异步的,而await关键字用于等待一个异步任务执行完成。
通过使用async和await,我们可以以同步的方式编写异步代码,使得代码更加清晰和易读。
使用async关键字声明的函数会返回一个Promise对象。在函数内部,我们可以使用await关键字来等待一个异步任务执行完成,而不需要使用回调函数或者Promise的then方法。当await关键字等待一个异步任务时,它会暂停函数的执行,并且等待异步任务完成后继续执行函数。
async和await的使用可以大大简化异步代码的编写,使得代码更易于理解和维护。它们是ES6中非常有用的特性,被广泛应用于JavaScript开发中。
引用: 目录 ES6的async和await关键字1、初步了解2、async关键字3、await关键字4、深入讲解async和await。 :主要介绍了详解ES6之async await 同步/异步方案,本文以最简明的方式来疏通 async await,有兴趣的可以了解下。 :我们先从字面意思来理解这两个关键字,async是asynchronous(异步)的简写,而await可以认为是async wait的简写。所以async可以理解为用于声明一个函数是异步的,而await用于等待一个异步任务执行完成。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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