# Constant Function
> Constant function.
A [constant function][constant-function] is a `function` whose output value is the same for every input value.
## 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
var v = fcn();
// returns 'beep'
v = fcn();
// returns 'beep'
```
## 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
```
## Examples
```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
}
```
[constant-function]: https://en.wikipedia.org/wiki/Constant_function