---
title: "check( val, sets, [tags] ) | Grafana k6 documentation"
description: "The jslib check function runs one or more checks on a value and generates a pass/fail result, but does not throw errors or interrupt test execution upon failure. It supports async values."
---

# check( val, sets, \[tags] )

The `check` function is a drop-in replacement for the built-in [check](/docs/k6/latest/javascript-api/k6/check/), with added support for async values. Any `Promise`s will be awaited, and the result is reported once the operation has been completed.

Expand table

| Parameter       | Type                         | Description                                                                               |
|-----------------|------------------------------|-------------------------------------------------------------------------------------------|
| val             | any                          | Value to test.                                                                            |
| sets            | Record<string, any>    | Tests (checks) to run on the value. Functions will be called. `Promise`s will be awaited. |
| tags (optional) | Record<string, string> | Extra tags to attach to metrics emitted.                                                  |

### Returns

Expand table

| Type    | Description |                                                                                                                                             |
|---------|-------------|---------------------------------------------------------------------------------------------------------------------------------------------|
| Promise | boolean     | `true` if all checks have succeeded, `false` otherwise. If any of the checked values was a `Promise`, the result is wrapped in a `Promise`. |

### Examples

Using `check()` with async values.

JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```javascript
import http from 'k6/http';
import { fail } from 'k6';
import { check } from 'https://jslib.k6.io/k6-utils/1.5.0/index.js';

function waitFor(delay) {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve(true);
    }, delay);
  });
}

export default async function () {
  const res = http.get('https://quickpizza.grafana.com/');

  const success = await check(res, {
    'passing promise as a value': waitFor(1000),
    'async function': async (res) => {
      await waitFor(500);

      return res.status === 200;
    },
  });

  if (!success) {
    fail('check did not succeed');
  }
}
```

For general usage of checks, refer to [check(val, set, \[tags\])](/docs/k6/latest/javascript-api/k6/check/#examples).