ajax：利用XMLHttpRequest建立到服务器的连接并处理返回信息
<html>
<head>
<script language="javascript" type="text/javascript">
function ajaxFunction()
{
var xmlHttp;
try
{
// Firefox,Opera 8.0+,Safari
xmlHttp=new XMLHttpRequest();
}
catch (e)
{
// Internet Explorer
try
{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
try
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e)
{
alert("您的浏览器不支持AJAX！");
return false;
}
}
}
/*以上浏览器类型的判定项也可等价为：
try{
if( window.ActiveXObject ){
for( var i = 5; i; i-- ){
try{
if( i == 2 ){ //IE
xmlhttp_request = new ActiveXObject( "Microsoft.XMLHTTP" ); }
else{
xmlhttp_request = new ActiveXObject( "Msxml2.XMLHTTP." + i + ".0" );
xmlhttp_request.setRequestHeader("Content-Type","text/xml");
xmlhttp_request.setRequestHeader("Charset","gb2312"); }
break;}
catch(e){
xmlhttp_request = false; } } }
else if( window.XMLHttpRequest ) //Firefox,Opera 8.0+,Safari
{ xmlhttp_request = new XMLHttpRequest();
if (xmlhttp_request.overrideMimeType)
{ xmlhttp_request.overrideMimeType('text/xml'); } } }
catch(e){ xmlhttp_request = false; }
*/
xmlHttp.onreadystatechange=function()
{
if(xmlHttp.readyState==4&&xmlHttp.status==200)//xmlHttp.status标示HTTP连接的状态
{
document.myForm.time.value=xmlHttp.responseText;
}
}
xmlHttp.open("GET","http://",true);
xmlHttp.send(null);
if(document.myForm.username.value.length==0)
alert(xmlHttp.responseText);
}
</script>
</head>
<body>
<form name="myForm" onSubmit="return ajaxFunction()" >
用户： <input type="text" name="username" >
时间： <input type="text" name="time" >
<input type="submit" name="button" value="提交">
</form>
</body>
</html>