1.引jquery包
<script type="text/javascript">
    $(function () {
        //根據學院動態填充專業
        $("[name=depart]").change(function () {
           var did= $(this).val();
           if (did==-1){
               alert("請選擇學院");
               $("[name=major]")[0].length=0;//[0]-->將jquery改為js
               $("[name=major]")[0].add(new option("請選擇",-1));//-->動態填充option復選框
           } else {
               $.ajax({
                   url: "/Educational/class/getallmajor",
                   data: "did" + did,
                   type: "post",
                   dataType: "json",
                   success: function (rs) {
                       $("[name=major]")[0].length=0;
                       $("[name=major]")[0].add(new option("請選擇",-1));
                       for (var i = 0; i < rs.length; i++) {
                           $("[name=major]")[0].add(new Option(rs[i].majorname, rs[i].majorid));
                       }
                   }
               })
           }
        })

 //動態確定班主任
$("[name=majorid]").change(function () {
  var did= $("[name=deptid]").val();
  var mid = $(this).val();
  if (mid==-1) {
      alert("請選擇專業");
  }
  $.ajax({
      url: "/Educational/class/getrolename",
      data: "did" + did+"&mid="+mid,
      type: "post",
      dataType: "json",
      success:function (rs) {
          $("[name=classteacher]")[0].length=0;
          for (var i = 0; i < rs.length; i++) {
              $("[name=classteacher]")[0].add(new Option(rs[i].userName, rs[i].userName));
          }
      }
  })
})

    })

jquery的ajax及註意事項