AJAX核心三部曲

//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.do?";
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;
}
}
}