---
layout: page
title: "JavaScript json_decode function"
comments: true
sharing: true
footer: true
alias:
- /functions/view/json_decode:456
- /functions/view/json_decode
- /functions/view/456
- /functions/json_decode:456
- /functions/456
---
<!-- Generated by Rakefile:build -->
A JavaScript equivalent of PHP's json_decode

{% codeblock json/json_decode.js lang:js https://raw.github.com/kvz/phpjs/master/functions/json/json_decode.js raw on github %}
function json_decode (str_json) {
  // From: http://phpjs.org/functions
  // +      original by: Public Domain (http://www.json.org/json2.js)
  // + reimplemented by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +      improved by: T.J. Leahy
  // +      improved by: Michael White
  // *        example 1: json_decode('[ 1 ]');
  // *        returns 1: true

  /*
    http://www.JSON.org/json2.js
    2008-11-19
    Public Domain.
    NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
    See http://www.JSON.org/js.html
  */

  var json = this.window.JSON;
  if (typeof json === 'object' && typeof json.parse === 'function') {
    try {
      return json.parse(str_json);
    } catch (err) {
      if (!(err instanceof SyntaxError)) {
        throw new Error('Unexpected error type in json_decode()');
      }
      this.php_js = this.php_js || {};
      this.php_js.last_error_json = 4; // usable by json_last_error()
      return null;
    }
  }

  var cx = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;
  var j;
  var text = str_json;

  // Parsing happens in four stages. In the first stage, we replace certain
  // Unicode characters with escape sequences. JavaScript handles many characters
  // incorrectly, either silently deleting them, or treating them as line endings.
  cx.lastIndex = 0;
  if (cx.test(text)) {
    text = text.replace(cx, function (a) {
      return '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
    });
  }

  // In the second stage, we run the text against regular expressions that look
  // for non-JSON patterns. We are especially concerned with '()' and 'new'
  // because they can cause invocation, and '=' because it can cause mutation.
  // But just to be safe, we want to reject all unexpected forms.
  // We split the second stage into 4 regexp operations in order to work around
  // crippling inefficiencies in IE's and Safari's regexp engines. First we
  // replace the JSON backslash pairs with '@' (a non-JSON character). Second, we
  // replace all simple value tokens with ']' characters. Third, we delete all
  // open brackets that follow a colon or comma or that begin the text. Finally,
  // we look to see that the remaining characters are only whitespace or ']' or
  // ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.
  if ((/^[\],:{}\s]*$/).
  test(text.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, '@').
  replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']').
  replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) {

    // In the third stage we use the eval function to compile the text into a
    // JavaScript structure. The '{' operator is subject to a syntactic ambiguity
    // in JavaScript: it can begin a block or an object literal. We wrap the text
    // in parens to eliminate the ambiguity.
    j = eval('(' + text + ')');

    return j;
  }

  this.php_js = this.php_js || {};
  this.php_js.last_error_json = 4; // usable by json_last_error()
  return null;
}
{% endcodeblock %}

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

### Example 1
This code
{% codeblock lang:js example %}
json_decode('[ 1 ]');
{% endcodeblock %}

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


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