js 动态添加事件

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>
  <TITLE> New Document </TITLE>
  <META NAME="Generator" CONTENT="EditPlus">
  <META NAME="Author" CONTENT="">
  <META NAME="Keywords" CONTENT="">
  <META NAME="Description" CONTENT="">
  <script>
 
 window.onload=function()
 {
  document.getElementById("sel").onchange=function(){setSel();};
 }

 function setSel()
 {
  var obj=document.getElementById("sel");
  if(obj.value=="2")
  {
   document.getElementById("sel2").value = "2";
  }
 }
  </script>
 </HEAD>

 <BODY>
  <div>
 <select id="sel">
  <option value="1">1
  <option value="2">2
  <option value="3">3
  <option value="4">4
 </select>

 <select id="sel2">
  <option value="1">1
  <option value="2">2
  <option value="3">3
  <option value="4">4
 </select>
  </div>
 </BODY>
</HTML>

原文地址:https://www.cnblogs.com/snlfq2000/p/1399035.html