Added reviver support to Asen's JSON.js

JSON.js

/**
 * Written by Asen Bozhilov
 * http://code.google.com/p/js-examples/source/browse/trunk/JSON.js
 */

if (!this.JSON) {
  this.JSON = {
    parse : (function (undefined) {
      var JSON_GRAMMAR = {
        STRING     : '"([^"\\x00-\\x1F\\\\]|\\\\["\\\\\/bfnrt]|\\\\u[0-9A-Fa-f]{4})*"',
        NUMBER     : '-?\\d+(?:\\.\\d+)?(?:[Ee][+-]?\\d+)?',
        BOOLEAN    : 'true|false',
        NULL       : 'null'
      },
      REG_EXP = {
        property      : new RegExp(JSON_GRAMMAR.STRING + '\\s*:', "g"),
        value         : new RegExp(JSON_GRAMMAR.STRING + '|' + JSON_GRAMMAR.NUMBER + '|' + JSON_GRAMMAR.BOOLEAN + '|' + JSON_GRAMMAR.NULL, "g"),
        invalidTokens : /[^{}\[\],\s]/
      },
      hasOwn = Object.prototype.hasOwnProperty,
      toString = Object.prototype.toString;

      return function(jsonStr, reviver) {
        var output;
        if (typeof jsonStr != 'string') {
          jsonStr = String(jsonStr);
        }
        if (!REG_EXP.invalidTokens.test(jsonStr.replace(REG_EXP.property,'').replace(REG_EXP.value, ''))) {
          output = eval('Array(null,' + jsonStr + ');');
          if (output.length == 2) {
            if (typeof reviver == 'function') {
              return walk({'':output[1]}, '');
            }
            return output[1];
          }
        }
        throw new SyntaxError('JSON.parse');

        // Walk operation described in 15.12.2
        function walk(holder, name) {
          var val = holder[name], // 1
          i, len, newElement;
          if (val && typeof val == 'object') { // 2
            if (toString.call(val) == '[object Array]') { // 2.a
              i = 0; // 2.a.i
              len = val.length; // 2.a.ii
              while (i < len) { // 2.a.iii
                newElement = walk(val, String(i)); // 2.a.iii.1
                if (newElement === undefined) { // 2.a.iii.2
                  delete val[i]; // 2.a.iii.2.a
                } else {
                  val[i] = newElement; // 2.a.iii.3.a
                }
                i++; // 2.a.iii.4
              }
            } else { // 2.b
              for (var p in val) { // 2.b.i, ii
                if (hasOwn.call(val, p)) {
                  newElement =  walk(val, p); // 2.b.ii.1
                  if (newElement === undefined) { // 2.b.ii.2
                    delete val[p]; // 2.b.ii.2.a
                  } else {
                    val[p] = newElement; // 2.b.ii.3.a
                  }
                }
              }
            }
          }
          return reviver.call(holder, name, val); // 3
        }
      };
    })()
  };
}