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# Constant Function

> Constant function.

<section class="intro">

A [constant function][constant-function] is a `function` whose output value is the same for every input value.

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var constantFunction = require( '@stdlib/utils/constant-function' );
```

#### constantFunction( x )

Returns a [constant function][constant-function] which always returns `x`.

```javascript
var fcn = constantFunction( 'beep' );
// returns <Function>

var v = fcn();
// returns 'beep'

v = fcn();
// returns 'beep'
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   When provided an object reference, the returned `function` always returns the same reference.

    ```javascript
    var obj = {};
    var fcn = constantFunction( obj );

    var bool = ( fcn() === obj );
    // returns true
    ```

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var constantFunction = require( '@stdlib/utils/constant-function' );

var bool;
var fcn;
var arr;
var v;
var i;

fcn = constantFunction( 3.14 );
for ( i = 0; i < 10; i++ ) {
    v = fcn();
    // returns 3.14
}

arr = [ 1, 2, 3 ];
fcn = constantFunction( arr );
for ( i = 0; i < 10; i++ ) {
    v = fcn();
    bool = ( v === arr );
    // returns true
}
```

</section>

<!-- /.examples -->

<section class="links">

[constant-function]: https://en.wikipedia.org/wiki/Constant_function

</section>

<!-- /.links -->