JS多级连动菜单

<meta http-equiv="Content-Type" content="text/html;charset=UTF-8"> <title>js联动下拉框</title> <meta name="generator" content="microsoft frontpage 4.0"> <meta name="progid" content="frontpage.editor.document"> <meta name="originator" content="microsoft visual studio .net 7.1"> <form name="form1" method="post">   <select id="s1" name="s1"><option selected></option></select><select id="s2" name="s2"><option selected></option></select><select id="s3" name="s3"><option selected></option></select><select id="x1" name="x1"><option selected></option></select><select id="x2" name="x2"><option selected></option></select><select id="x3" name="x3"><option selected></option></select><select id="x4" name="x4"><option selected></option></select><select id="x5" name="x5"><option selected></option></select> </form>
[ctrl+a 全选 注:如需引入外部js需刷新才能执行]