that specifies the object or collection to retrieve. If this parameter is an integer, it is the zero-based index of the object. If this parameter is a string, all objects with matching name or id properties are retrieved, and a collection is returned if more than one match is made.
当第一个参数为字符时,查找相匹配的名称,如果第一个参数为数值,根据索引返回.