# ★ isFalse()

## `isFalse()`

Checks if [`any`](https://www.typescriptlang.org/docs/handbook/2/everyday-types.html#any) value is a [`boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) type or an instance of [`Boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) by using [`isBoolean()`](/type/is/isboolean.md) function, that is equal to `false`.

{% code title="is-false.func.ts" %}

```typescript
const isFalse = <Payload extends object>(
  value: any,
  callback: ResultCallback<any, Payload> = resultCallback,
  payload?: Payload
): value is false =>
  callback(
    isBoolean(value) ? value.valueOf() === false : false,
    value,
    payload
  );
```

{% endcode %}

### Generic type variables

#### <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`](/type/type/resultcallback.md#payload-payload) of the supplied [`callback`](#callback-resultcallback-less-than-any-payload-greater-than) function and [`payload`](#payload-payload) optional parameter of the [`isFalse()`](#isfalse) function from which it captures its value.

### Parameters

#### `value: any`

The value of [`any`](https://www.typescriptlang.org/docs/handbook/2/everyday-types.html#any) type to check.

#### `callback: ResultCallback<any, Payload>`

A callback `function` of [`ResultCallback`](/type/type/resultcallback.md) type with parameters, the [`value`](#value-any) that has been checked, the [`result`](/type/type/resultcallback.md#result-boolean) of this check, and [`payload`](/type/type/resultcallback.md#payload-payload) of generic type variable [`Payload`](#payloadextendsobject) with optional properties from the provided [`payload`](#payload-payload), to handle them before the [`result`](/type/type/resultcallback.md#result-boolean) return. By default, it uses [`resultCallback()`](/type/helper/resultcallback.md) 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`](/type/type/resultcallback.md#payload-payload) of the given [`callback`](#callback-resultcallback-less-than-any-payload-greater-than) function.

### Return type

#### `value is false`

The **return type** is a [`boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) as the result of its statement, indicating the [`value`](#value-any) is equal to `false`.

### Returns

The **return value** is a [`boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) indicating whether the provided [`value`](#value-any) is a [`boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) type or an instance of [`Boolean`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) that is equal to `false`.

## Example usage

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

isFalse(true); // Returns `false` as `value is false`
isFalse(false); // Returns `true` as `value is false`

isFalse(new Boolean(true)); // Returns `false` as `value is false`
isFalse(new Boolean(false)); // Returns `true` as `value is false`
```

### Parameters `callback` and `payload`

```typescript
// Callback and payload parameters example usage.
import { isFalse } from '@angular-package/type';

isFalse(new Boolean(false), (result, value, payload) => {
  value // Returns `Boolean {false}`
  if (payload) {
    result // Returns `false`
    payload.age // Returns `27`
  }
  return result;
}, { age: 27 }); // Returns `true` as `value is false`
```


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