//对象克隆

        function clone(obj) {

            // Handle the 3 simple types, and null or undefined

            if (null == obj || "object" != typeof obj) return obj;

            // Handle Date

            if (obj instanceof Date) {

                var copy = new Date();

                copy.setTime(obj.getTime());

                return copy;

            }

            // Handle Array

            if (obj instanceof Array) {

                var copy = [];

                var len = obj.length;

                for (var i = 0; i < len; ++i) {

                    copy[i] = clone(obj[i]);

                }

                return copy;

            }

            // Handle Object

            if (obj instanceof Object) {

                var copy = {};

                for (var attr in obj) {

                    if (obj.hasOwnProperty(attr)) copy[attr] = clone(obj[attr]);

                }

                return copy;

            }

            throw new Error("Unable to copy obj! Its type isn't supported.");

        }