AJAX 核心三部曲

<script lanuage = "javaScript">

//建立對象
function createXMLHttpRequest(){
 if(window.ActiveXObject){
  xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");    
 }
 else if(window.XMLHttpRequest){
  xmlHttp = new XMLHttpRequest();
 }
}

//前台介面事件調用的函數
function checkName(){
 createXMLHttpRequest();
 xmlHttp.onreadystatechange = handleStateChange;
 var sql = "UserReg.aspx?";
 xmlHttp.open("GET",sql,true);
 xmlHttp.send(null);
}

//和伺服器互動期間執行的函數
function handleStateChange(){
 if(xmlHttp.readyState == 4){
  if(xmlHttp.status == 200){   
  document.getElementById("divx").innerHTML = xmlHttp.responseText;
  }
 }
}

<script>