从setTimeout获取返回值

本文介绍了从setTimeout获取返回值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我只想从setTimeout获取返回值，但我得到的是该函数的整个文本格式？

I just want to get the return value from setTimeout but what i get is a whole text format of the function?

function x () { setTimeout(y = function () { return 'done'; }, 1000); return y; } console.log(x());

推荐答案

您需要使用Promises。它们是在ES6中提供，但可以是polyfilled 非常轻松：

You need to use Promises for this. They are available in ES6 but can be polyfilled quite easily:

function x() { var promise = new Promise(function(resolve, reject) { window.setTimeout(function() { resolve('done!'); }); }); return promise; } x().then(function(done) { console.log(done); // --> 'done!' });

async / 等待在ES2017中如果在 async 函数内变得更好：

With async/await in ES2017 it becomes nicer if inside an async function:

async function() { const result = await x(); console.log(result); // --> 'done!'; }