var xmlHttp;

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


function validate(n){
	createXMLHttpRequest();
	switch(n)
	 {
	 case 1://用户名
	 var username = document.getElementById("username");
	 var url = "ajax_reg.php?username=" + username.value + "&n=" + n + "&t=" + new Date().getTime();
	 break;
	 case 2://邮件
	 var mail = document.getElementById("mail");
	 var url = "ajax_reg.php?mail=" + mail.value + "&n=" + n + "&t=" + new Date().getTime();
	 break;
	 }
	
	xmlHttp.open("GET",url,true);
	xmlHttp.onreadystatechange = callback;
	xmlHttp.send(null);
}



function callback(){
	if(xmlHttp.readyState == 4){
		if(xmlHttp.status == 200){
			var val = xmlHttp.responseText;
			setMessage(val);
		}
	}
}

function setMessage(isValid){
	var messageArea;
	var fontColor = "#FF0000";
	var message = "*";
	switch(isValid){
		case "11":
	 	messageArea = document.getElementById("u");
		fontColor = "#0d58a5";
		message = "此用户名可以注册";
	 	break;	
		case "12":
	 	messageArea = document.getElementById("u");
		fontColor = "#FF0000";
		message = "此用户名已经被注册，请更换用户名";
	 	break;	
		case "10":
	 	messageArea = document.getElementById("u");
		fontColor = "#FF0000";
		message = "必填项";
	 	break;	
		case "21":
	 	messageArea = document.getElementById("m");
		fontColor = "#0d58a5";
		message = "此邮件可以注册";
	 	break;	
		case "22":
	 	messageArea = document.getElementById("m");
		fontColor = "#FF0000";
		message = "此邮件已经被注册，请更换邮件地址";
	 	break;
		case "20":
	 	messageArea = document.getElementById("m");
		fontColor = "#FF0000";
		message = "必填项";
	 	break;
		
	}
	messageArea.style.color = fontColor;
	messageArea.innerHTML = message;
}