clone object without reference

clone.js

        // clone object without reference
        // http://stackoverflow.com/questions/728360/most-elegant-way-to-clone-a-javascript-object
        function clone(obj) {
            var copy;

            // Handle the 3 simple types, and null or undefined
            if (null == obj || "object" != typeof obj) return obj;

            // Handle Date
            if (obj instanceof Date) {
                copy = new Date();
                copy.setTime(obj.getTime());
                return copy;
            }

            // Handle Array
            if (obj instanceof Array) {
                copy = [];
                for (var i = 0, len = obj.length; i < len; i++) {
                    copy[i] = clone(obj[i]);
                }
                return copy;
            }

            // Handle Object
            if (obj instanceof Object) {
                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.");
        }