var xmlHttp;
function createXMLHttpRequest(){
	if(window.ActiveXObject)
		xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
	else if(window.XMLHttpRequest)
		xmlHttp = new XMLHttpRequest();
}
function showResult(sText){
	var oSpan = document.getElementById("Result");
	oSpan.innerHTML = sText;
	if(sText.indexOf("已經存在") >= 0)
		//如果用戶名已被占用
		oSpan.style.color = "red";
	else
		oSpan.style.color = "black";
}
function startCheck(oInput){
	//首先判斷是否有輸入，沒有輸入直接返回，並提示
	if(!oInput.value){
		oInput.focus();		//聚焦到用戶名的輸入框
		document.getElementById("Result").innerHTML = "<span style='color:#ff0000'>信箱不可空白</span>";
		return;
	}
	//建立非同步請求
	createXMLHttpRequest();
	var sUrl = "9-9.php?email=" + oInput.value.toLowerCase() + "&timestamp=" + new Date().getTime();
	xmlHttp.open("GET",sUrl,true);
	xmlHttp.onreadystatechange = function(){
		if(xmlHttp.readyState == 4 && xmlHttp.status == 200)
			showResult(xmlHttp.responseText);	//顯示服務器結果
	}
	xmlHttp.send(null);
}