# How to slow down a loop in JavaScript

> Learn how to slow down a loop in JavaScript by building a sleep() function with a promise and setTimeout, then awaiting it inside a for...of loop.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2020-04-15 | Topics: [JavaScript](https://flaviocopes.com/tags/js/) | Canonical: https://flaviocopes.com/how-to-slow-loop-javascript/

I had a loop where I wanted to call an API multiple times, e.g. 500 times.

APIs implement rate limiting and even if not, it's just unkind to make those many requests in a very short time.

So I wanted to slow down the loop. How?

Turns out it's pretty simple, once you set up a sleep() function, that you don't need to change:

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

Then you can call `await sleep(1000)` to stop 1 second in every iteration, like this:

```js
const list = [1, 2, 3, 4]
const doSomething = async () => {
  for (const item of list) {
    await sleep(1000)
    console.log('🦄')    
  }
}

doSomething()
```