Decode Json

[Requenaeo]

Hola migo acá necesito un ayuda con Json, bueno para Json soy algo novato pero voy aprendiendo poco a poco así que mi duda es con un decode de Json a partir de javascript, ya que en php ya le resulto, vean

Código HTML:

\u003Cdiv\u003EHola\u003E\u003C\/div\u003E
 

esto es encode de un simple div por php y lo que quiero es que cuando sea solicitado por script le envié la consulta a un php y de resulta sea lo que mostré y que el script decode ese archivo pero se me ha hecho complicado. Lo que he buscado por internet ese este script

Código Javascript:

function json_decode(str_json) {
  //       discuss at: http://phpjs.org/functions/json_decode/
  //      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: [1]
 
  /*
       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 || {};
      // usable by json_last_error()
      this.php_js.last_error_json = 4;
      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 || {};
  // usable by json_last_error()
  this.php_js.last_error_json = 4;
  return null;
}
 

pero aun no se dominarlo
por favor si hay alguien que me ayuda, se lo agradezco ante amno.