javascript克隆一个对象

/*
 * 克隆一个对象
 */
com.ty.repairtech.JsonOperation.clone = function(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 = [];
        for (var i = 0, len = obj.length; i < len; ++i) {
            copy[i] = com.ty.repairtech.JsonOperation.clone(obj[i]);
        }
        return copy;
    }
    // Handle Object
    if ( obj instanceof Object) {
        var copy = {};
        for (var attr in obj) {
            if (obj.hasOwnProperty(attr))
                copy[attr] = com.ty.repairtech.JsonOperation.clone(obj[attr]);
        }
        return copy;
    }
    throw new Error("Unable to copy obj! Its type isn't supported.");
}