JavaScript Thread.Sleep()

布衣过冬夏 · 发表于 2019-7-12 17:00:00

What is the JavaScript version of sleep()?

需要注意的是，这里必须await才会等待

Since 2009 when this question was asked, JavaScript has evolved significantly. All other answers are now obsolete or overly complicated. Here is the current best practice:

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function demo() {
  console.log('Taking a break...');
  await sleep(2000);
  console.log('Two seconds later, showing sleep in a loop...');

  // Sleep in loop
  for (let i = 0; i < 5; i++) {
    if (i === 3)
      await sleep(2000);
    console.log(i);
  }
}

demo();

This is it. `await sleep(<duration>)`.

Note that,

await can only be executed in functions prefixed with the async keyword, or at the top level of your script in some environments (e.g. the Chrome DevTools console, or Runkit).
await only pauses the current async function

Two new JavaScript features helped write this "sleep" function:

Promises, a native feature of ES2015 (aka ES6). We also use arrow functions in the definition of the sleep function.
The async/await feature lets the code explicitly wait for a promise to settle (resolve or reject).

Compatibility

promises are supported in Node v0.12+ and widely supported in browsers, except IE
async/await landed in V8 and has been enabled by default since Chrome 55 (released in Dec 2016)
- it landed in Node 7 in October 2016
- and also landed in Firefox Nightly in November 2016

If for some weird reason you're using Node older than 7 (which has reached end of life), or are targeting old browsers, async/await can still be used via Babel (a tool that will transpile JavaScript + new features into plain old JavaScript), with the transform-async-to-generator plugin.

What's the equivalent of Java's Thread.sleep() in JavaScript? [duplicate]

The simple answer is that there is no such function.

The closest thing you have is:

var millisecondsToWait = 500;
setTimeout(function() {
    // Whatever you want to do after the wait
}, millisecondsToWait);

Note that you especially don't want to busy-wait (e.g. in a spin loop), since your browser is almost certainly executing your JavaScript in a single-threaded environment.

Here are a couple of other SO questions that deal with threads in JavaScript:

JavaScript and Threads
Why doesn't JavaScript support multithreading?

And this question may also be helpful:

setTimeout - how to avoid using string for callback?

How to wait 5 seconds with jQuery?

Built in javascript setTimeout.

setTimeout(
  function() 
  {
    //do something special
  }, 5000);

UPDATE: you want to wait since when the page has finished loading, so put that code inside your $(document).ready(...); script.

UPDATE 2: jquery 1.4.0 introduced the .delay method. Check it out. Note that .delay only works with the jQuery effects queues.

来源：https://www.cnblogs.com/chucklu/p/11177148.html