您好我有两个链接的下拉菜单栏。在第一个选项中，我有一个服务器名称列表，在第二个选项中，我有一个与每个服务器名称关联的文件名列表。
示例代码：
var categories = [];
categories["startList"] = ["WEL0282","WEL0855","WEL0703","WEL0704","WEL0706","WEL0707"]
categories["WEL0855"] = ["WEL_log_2014_04.zip","WEL_log_2014_05.xls"];
categories["WEL0282"] = ["WEL_log_2013_10.zip","WEL_log_2013_11.zip",
"WEL_log_2013_12.zip","WEL_log_2014_01.zip",
"WEL_log_2014_02.zip","WEL_log_2014_03.zip",
"WEL_log_2014_04.zip","WEL_log_2014_05.xls"];
我需要一个动态数组，只有当前月份的文件名应该是.xls，前几个月的文件名应该是.zip文件。请帮助我如何做到这一点。