# bun/prefer-builtin-sleep

> Prefer `Bun.sleep()` to a promise that only waits for `setTimeout`

`new Promise(resolve => setTimeout(resolve, ms))` takes a moment to read, and all it does is wait. `Bun.sleep(ms)` does the same thing and says so. `setTimeout(ms)` from `node:timers/promises` does too.

`--fix-suggestions` replaces the promise with `Bun.sleep(ms)`.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"bun/prefer-builtin-sleep" = "error" # or "warn"
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad */}
```js
await new Promise(resolve => setTimeout(resolve, 500));
```

{/* bad */}
```js
function wait(ms) {
  return new Promise(resolve => {
    setTimeout(() => resolve(), ms);
  });
}
```

Not reported:

{/* good */}
```js
await Bun.sleep(500);
```

{/* good */}
```js
import { setTimeout } from "node:timers/promises";

await setTimeout(500);
```

A promise that does more than wait isn't reported. This one resolves with a value:

{/* good */}
```js
const answer = await new Promise(resolve => setTimeout(() => resolve("timed out"), 500));
```

## When not to use it

`Bun.sleep()` only exists in Bun, and `node:timers/promises` doesn't exist in browsers. Turn the rule off for code that also runs in a browser.