json check and eval

json.js

function json(str) {
	var _str = str;
	var innermostObjectReg = /(^|[[:,])\s*(?:\[(?:\s*(?:"(?:\\["\\/bfnrt]|\\u[0-9A-Fa-f]{4}|[^\\"])*"|-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[Ee][+-]?\d+)?|true|false|null)\s*(?:,\s*(?:"(?:\\["\\/bfnrt]|\\u[0-9A-Fa-f]{4}|[^\\"])*"|-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[Ee][+-]?\d+)?|true|false|null)\s*)*|\s*)\]|\{(?:\s*"(?:\\["\\/bfnrt]|\\u[0-9A-Fa-f]{4}|[^\\"])*"\s*:\s*(?:"(?:\\["\\/bfnrt]|\\u[0-9A-Fa-f]{4}|[^\\"])*"|-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[Ee][+-]?\d+)?|true|false|null)\s*(?:,\s*"(?:\\["\\/bfnrt]|\\u[0-9A-Fa-f]{4}|[^\\"])*"\s*:\s*(?:"(?:\\["\\/bfnrt]|\\u[0-9A-Fa-f]{4}|[^\\"])*"|-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[Ee][+-]?\d+)?|true|false|null)\s*)*|\s*)\})\s*(?=[\]},]|$)/g;
	while (_str !== (_str = _str.replace(innermostObjectReg, '$10')));

	if (/^\s*(?:"(?:\\["\\/bfnrt]|\\u[0-9A-Fa-f]{4}|[^\\"])*"|-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[Ee][+-]?\d+)?|true|false|null)\s*$/.test(_str)) {
		_str = str.replace(/\u2028|\u2029/g, function(c) {
			return c === '\u2028' ? '\\u2028' : '\\u2029';
		});
		return eval('(' + _str + ')');
	}

	return null;
}