/*
	通过Ajax，根据t编号获取相应的科目信息，
	过滤科目列表
*/
function getHTTPObject() {
	var xmlhttp = false;
	if (window.XMLHttpRequest) {
		xmlhttp = new XMLHttpRequest();
		if (xmlhttp.overrideMimeType) {
			xmlhttp.overrideMimeType("text/xml");
		}
	} else {
		try {
			xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch (e) {
			try {
				xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch (e) {
				xmlhttp = false;
			}
		}
	}
	return xmlhttp;
}
var myXMLHttp = getHTTPObject();


function changeList(path,obj, obj2) {
	var value = obj.value;
	var url = path+"&"+obj.name+"=" + value + "&random=" + Math.random();
	myXMLHttp.open("GET", url, true);
	myXMLHttp.onreadystatechange = function () {
		handleHttpResponse(document.getElementById(obj2));
	};
	myXMLHttp.send();
}
function handleHttpResponse(object) {
	if (myXMLHttp.readyState == 4) {
		if (200 == myXMLHttp.status) {
			var subjectValue = object.value;
			object.length = 0;
			object.options[0] = new Option("--\u8bf7\u9009\u62e9--", "-1");
			var str = myXMLHttp.responseText;
			var o = eval(str);
			if(o==null||o.length == "undefined"){
				return;
			}
			for (var i = 0; i < o.length; i++) {
				object.options[object.options.length] = new Option(o[i].NAME, o[i].ID);
				if(o[i].ID == subjectValue){
					object.selectedIndex = i+1;
				}
			}
			return "complete";
		} else {
			if (500 == myXMLHttp.status) {
				alert("\u5185\u90e8\u670d\u52a1\u51fa\u9519!");
			} else {
				if (404 == myXMLHttp.status) {
					alert("\u627e\u4e0d\u5230\u7f51\u9875!");
				}
			}
		}
	}
}