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

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?

Try with this code. I hope it's useful for you.

function sleep(seconds) 
{
  var e = new Date().getTime() + (seconds * 1000);
  while (new Date().getTime() <= e) {}
}

Assuming you're able to use ECMAScript 2017 you can emulate similar behaviour by using async/await and setTimeout. Here's an example sleep function:

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

You can then use the sleep function in any other async function like this:

async function testSleep() {
    console.log("Waiting for 1 second...");
    await sleep(1000);
    console.log("Waiting done."); // Called 1 second after the first console.log
}

This is nice because it avoids needing a callback. The down side is that it can only be used in async functions. Behind the scenes the testSleep function is paused, and after the sleep completes it is resumed.

From MDN:

The await expression causes async function execution to pause until a Promise is fulfilled or rejected, and to resume execution of the async function after fulfillment.

For a full explanation see:

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await