# isRegExp

Evaluates whether the given value is of type [RegExp](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp)

```javascript
import isRegExp from 'deep-waters/isRegExp';

isRegExp(/^foo$/); // → true
isRegExp(new RegExp(/^foo$/)); // → true

isRegExp("/^foo$/"]); // → false
isRegExp(null); // → false
isRegExp("foo"); // → false
```

*isRegExp*, like any other type validator, is mostly used in [composed](https://antonioru.gitbook.io/deep-waters/type-validators/broken-reference) validators:

```javascript
import isString from 'deep-waters/isString';
import matchesPattern from 'deep-waters/matchesPattern';

const isEmail = compose(
  isString,
  matchesPattern(/^\w+([.-]?\w+)*@\w+([.-]?\w+)*(\.\w{2,3})+$/),
);
```

{% hint style="success" %}
**isRegExp** is built on top of [ofClass](https://antonioru.gitbook.io/deep-waters/validators/ofclass) validator and rely on `Object.prototype.toString` to check on the received value type in order to avoid [typeof weird behaviours ](https://stackoverflow.com/questions/18808226/why-is-typeof-null-object)and encouraging a **runtime strict type validation**.
{% endhint %}