# guardRegExp()

## `guardRegExp()`

Guards the value to be a [`RegExp`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp).

{% code title="guard-regexp.func.ts" %}

```typescript
const guardRegExp = <Type extends RegExp, Payload extends object>(
  value: Type,
  callback?: ResultCallback<Type, Payload>,
  payload?: Payload
): value is Type => isRegExp(value, callback, payload);
```

{% endcode %}

{% embed url="<https://github.com/angular-package/type/blob/main/src/guard/lib/guard-regexp.func.ts>" %}

### Generic type variables

#### <mark style="color:green;">**`Type`**</mark>**`extends`**<mark style="color:green;">**`RegExp`**</mark>

A generic type variable `Type` constrained by [`RegExp`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp) indicates captured type of the given [`value`](#value-type) via the [return type](#return-type) and the [`value`](https://type.angular-package.dev/type-draft/type/resultcallback#value-value) parameter of the provided [`callback`](#callback-resultcallback-less-than-type-payload-greater-than) function [`ResultCallback`](https://type.angular-package.dev/type-draft/type/resultcallback) type.

#### <mark style="color:green;">**`Payload`**</mark>**`extends`**<mark style="color:green;">**`object`**</mark>

The `Payload` generic type variable constrained by [`object`](https://www.typescriptlang.org/docs/handbook/basic-types.html#object) indicates the type of optional parameter [`payload`](https://type.angular-package.dev/type-draft/type/resultcallback#payload-payload) of the supplied [`callback`](#callback-resultcallback-less-than-type-payload-greater-than) function and [`payload`](#payload-payload) optional parameter of the [`guardRegExp()`](#guardregexp) function from which it captures its value.

### Parameters

#### `value: Type`

Regular expression of generic type variable [`Type`](#typeextendsregexp) constrained by [`RegExp`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp) to guard.

#### `callback?: ResultCallback<Type, Payload>`

The optional callback [`function`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Functions) of [`ResultCallback`](https://type.angular-package.dev/type-draft/type/resultcallback) type with parameters, the [`value`](#value-type) that has been checked, the `result` of this check, and `payload` of generic type variable [`Payload`](#payloadextendsobject) with optional properties from the provided `payload`, to handle them before the `result` return. By default, it uses `resultCallback()` function.

#### `payload?: Payload`

An optional [`object`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object) of the generic type variable [`Payload`](#payloadextendsobject) is assigned to the [`payload`](https://type.angular-package.dev/type-draft/type/resultcallback#payload-payload) of the given [`callback`](#callback-resultcallback-less-than-type-payload-greater-than) function.

### Return type

#### `value is Type`

The **return type** is a [`boolean`](https://www.typescriptlang.org/docs/handbook/basic-types.html#boolean) as the result of its statement indicating the [`value`](#value-type) is a generic type variable [`Type`](#typeextendsregexp), by default of type captured from the supplied [`value`](#value-type).&#x20;

### Returns

The **return value** is a [`boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) indicating whether the [`value`](#value-type) is a [`RegExp`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp).

## Example usage

```typescript
// Example usage.
import { guardRegExp } from '@angular-package/type';

guardRegExp(/^[]/); // true, value is RegExp
guardRegExp(false as any); // false, value is RegExp
```