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
}
doSomething()
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.