javascript 是否有返回 ES6 承诺的 setTimeout 版本？
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Is there a version of setTimeout that returns an ES6 promise?
提问by Michael Kropat
Similar to this question, but rather than asking about how promises work in general, I specifically want to know:
与this question类似，但不是询问promises一般是如何工作的，我特别想知道：
What is the standard/best way to wrap setTimeoutin something that returns a Promise? I'm thinking something like Angular's $timeoutfunction, but not Angular specific.
在返回Promise 的东西中包装setTimeout的标准/最佳方法是什么？我在想像 Angular's function这样的东西，但不是 Angular 特有的。$timeout
回答by Benjamin Gruenbaum
In Browsers
在浏览器中
First of all no - there is no built in for this. Lots of libraries that enhance ES2015 promises like bluebird whip with it.
首先不 - 没有为此内置。许多增强 ES2015 的库就像 bluebird 鞭子一样。
I think the other answer conflates executing the function and a delay, it also creates timeouts that are impossible to cancel. I'd write it simply as:
我认为另一个答案将执行函数和延迟混为一谈，它还创建了无法取消的超时。我会简单地写成：
function delay(ms){
var ctr, rej, p = new Promise(function (resolve, reject) {
ctr = setTimeout(resolve, ms);
rej = reject;
});
p.cancel = function(){ clearTimeout(ctr); rej(Error("Cancelled"))};
return p;
}
Then you can do:
然后你可以这样做：
delay(1000).then(/* ... do whatever */);
Or
或者
doSomething().then(function(){ return delay(1000); }).then(doSomethingElse);
If we only want the basic functionality in ES2015, it's even simpler as:
如果我们只想要 ES2015 中的基本功能，那就更简单了：
let delay = ms => new Promise(r => setTimeout(r, ms));
In Node
在节点
You can use util.promisifyon setTimeoutto get a delayfunction back - meaning you don't have to use the new Promiseconstructor anymore.
您可以使用util.promisifyonsetTimeout返回一个delay函数——这意味着您不必再使用new Promise构造函数。
回答by Michael Kropat
Here's how I'd implement it:
这是我如何实现它：
function delay(duration, func) {
var args = Array.prototype.slice.call(arguments, 2);
return new Promise(function (resolve) {
setTimeout(function () {
resolve(func.apply(null, args));
}, duration);
});
}
(ES5-syntax intentionally chosen)
（有意选择 ES5 语法）
But maybe there's a common library that already does this, or a better way to do it.
但也许有一个公共库已经这样做了，或者有更好的方法来做到这一点。
回答by vitalets
If you need the proper cancellation of promised timeoutsimilar to clearTimeout- returning the promise directly from setTimeoutis not convenient. Especially when using with ES7 async / awaitin try...finallyblock. It is better to have separate variable for timeout manipulation. I've implemented this approach as tiny await-timeoutpackage. It works as following:
如果您需要正确取消承诺超时类似于clearTimeout- 直接从承诺返回setTimeout是不方便的。特别是在块中使用ES7 async / await时try...finally。最好有单独的变量用于超时操作。我已经将这种方法实现为微小的等待超时包。它的工作原理如下：
import Timeout from 'await-timeout';
async function foo() {
const timeout = new Timeout();
try {
const fetchPromise = fetch('https://example.com');
const timerPromise = timeout.set(1000).then(() => console.log('Timeout!'));
await Promise.race([fetchPromise, timerPromise]);
} finally {
timeout.clear();
}
}
In this example timeout will definitely be cleared in case of fetch success or any error and console.log('Timeout!')will not be called.
在这个例子中，超时肯定会在获取成功或任何错误的情况下被清除，并且console.log('Timeout!')不会被调用。
