jQuery方法扩展：type, toJSON, evalJSON

(function($) { 
    // the code of this function is from  
    // http://lucassmith.name/pub/typeof.html 
    $.type = function(o) { 
        var _toS = Object.prototype.toString; 
        var _types = { 
            'undefined': 'undefined', 
            'number': 'number', 
            'boolean': 'boolean', 
            'string': 'string', 
            '[object Function]': 'function', 
            '[object RegExp]': 'regexp', 
            '[object Array]': 'array', 
            '[object Date]': 'date', 
            '[object Error]': 'error' 
        }; 
        return _types[typeof o] || _types[_toS.call(o)] || (o ? 'object' : 'null'); 
    }; 
    // the code of these two functions is from mootools 
    // http://mootools.net 
    var $specialChars = { '\b': '\\b', '\t': '\\t', '\n': '\\n', '\f': '\\f', '\r': '\\r', '"': '\\"', '\\': '\\\\' }; 
    var $replaceChars = function(chr) { 
        return $specialChars[chr] || '\\u00' + Math.floor(chr.charCodeAt() / 16).toString(16) + (chr.charCodeAt() % 16).toString(16); 
    }; 
    $.toJSON = function(o) { 
        var s = []; 
        switch ($.type(o)) { 
            case 'undefined': 
                return 'undefined'; 
                break; 
            case 'null': 
                return 'null'; 
                break; 
            case 'number': 
            case 'boolean': 
            case 'date': 
            case 'function': 
                return o.toString(); 
                break; 
            case 'string': 
                return '"' + o.replace(/[\x00-\x1f\\"]/g, $replaceChars) + '"'; 
                break; 
            case 'array': 
                for (var i = 0, l = o.length; i < l; i++) { 
                    s.push($.toJSON(o[i])); 
                } 
                return '[' + s.join(',') + ']'; 
                break; 
            case 'error': 
            case 'object': 
                for (var p in o) { 
                    s.push(p + ':' + $.toJSON(o[p])); 
                } 
                return '{' + s.join(',') + '}'; 
                break; 
            default: 
                return ''; 
                break; 
        } 
    }; 
    $.evalJSON = function(s) { 
        if ($.type(s) != 'string' || !s.length) return null; 
        return eval('(' + s + ')'); 
    }; 
})(jQuery);