---
layout: page
title: "JavaScript function_exists function"
comments: true
sharing: true
footer: true
alias:
- /functions/view/function_exists:408
- /functions/view/function_exists
- /functions/view/408
- /functions/function_exists:408
- /functions/408
---
<!-- Generated by Rakefile:build -->
A JavaScript equivalent of PHP's function_exists

{% codeblock funchand/function_exists.js lang:js https://raw.github.com/kvz/phpjs/master/functions/funchand/function_exists.js raw on github %}
function function_exists (func_name) {
  // From: http://phpjs.org/functions
  // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +   improved by: Steve Clay
  // +   improved by: Legaev Andrey
  // +   improved by: Brett Zamir (http://brett-zamir.me)
  // *     example 1: function_exists('isFinite');
  // *     returns 1: true

  if (typeof func_name === 'string') {
    func_name = this.window[func_name];
  }
  return typeof func_name === 'function';
}
{% endcodeblock %}

 - [Raw function on GitHub](https://github.com/kvz/phpjs/blob/master/functions/funchand/function_exists.js)

Please note that php.js uses JavaScript objects as substitutes for PHP arrays, they are 
the closest match to this hashtable-like data structure. 

Please also note that php.js offers community built functions and goes by the 
[McDonald's Theory](https://medium.com/what-i-learned-building/9216e1c9da7d). We'll put online 
functions that are far from perfect, in the hopes to spark better contributions. 
Do you have one? Then please just: 

 - [Edit on GitHub](https://github.com/kvz/phpjs/edit/master/functions/funchand/function_exists.js)

### Example 1
This code
{% codeblock lang:js example %}
function_exists('isFinite');
{% endcodeblock %}

Should return
{% codeblock lang:js returns %}
true
{% endcodeblock %}


### Other PHP functions in the funchand extension
{% render_partial _includes/custom/funchand.html %}