Ajax 脚本模板--表单验证

var xmlHttp;

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

function validate(field){
	if(field.value != ""){
		createXMLHttpRequest();
		var url = "user_validate.jsp?userId=" + field.value + "&timestamp=" + new Date().getTime();
		xmlHttp.open("GET", url, true);
		xmlHttp.onreadystatechange=callBack;
		xmlHttp.send(null);
	}else {
		document.getElementById("userIdSpan").innerHTML="";
	}
}

function callBack(){
	if(xmlHttp.readyState == 4){
		if(xmlHttp.status == 200){
			document.getElementById("userIdSpan").innerHTML=xmlHttp.responseText;
		} else {
			alert("xmlHttp 请求失败，错误码 " + xmlHttp.status);
		}
	}
}