Sometimes you want your function to pause execution for a fixed amount of seconds or milliseconds.

In a programming language like C or PHP, you’d call sleep(2) to make the program halt for 2 seconds. Java has Thread.sleep(2000), Python has time.sleep(2), Go has time.Sleep(2 * time.Second).

JavaScript does not have a native sleep function, but thanks to the introduction of promises (and async/await in ES2018) we can implement such feature in a very nice and readable way, to make your functions sleep:

const sleep = (milliseconds) => {
  return new Promise(resolve => setTimeout(resolve, milliseconds))

You can now use this with the then callback:

sleep(500).then(() => {
  //do stuff

Or use it in an async function:

const doSomething = async () => {
  await sleep(2000)
  //do stuff


Remember that due to how JavaScript works, this does not pause the entire program execution like it might happen in other languages, but instead only your function sleeps.

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