// Ajax应用常用功能函数
//返回一个XMLHttpRequest对象
function getHttpRequest(){
	var obj = null;
	if(window.ActiveXObject){
		obj = new ActiveXObject("Microsoft.XMLHTTP");
	}else if(window.XMLHttpRequest){
		obj = new XMLHttpRequest();
	}else{
		var e = new Error("浏览器不支持XMLHttpRequest对象!")
		throw e;
	}
	return obj;
}

//创建一个显示加载错误的option
function createDispErrOption(txt){
	var opt = document.createElement("option");
	opt.appendChild(document.createTextNode("错误:"+txt));
	opt.setAttribute("value","");
	return opt;
}

//创建一个显示数据加载加的option
function createDispWaitOption(){
	var opt = document.createElement("option");
	opt.appendChild(document.createTextNode("数据加载中..."));
	opt.setAttribute("value","");
	return opt;
}

//清除一个DOM对象的所有子对象
function clearChildrenNodes(obj){
	for(var i = obj.childNodes.length-1;i >= 0;i--)obj.removeChild(obj.childNodes[i]);
}

//创建一个option对象
function createOption(txt,val){
	var opt = document.createElement("option");
	opt.setAttribute("value",val);
	opt.appendChild(document.createTextNode(txt));
	return opt;
}

//返回页面DOM对象
function $(objid){
	return document.getElementById(objid);
}
function $$(objname){
	if(window.ActiveXObject){
		var objs = new Array();
		var nonedivs = document.getElementsByName(objname);
		for(var i=0;i<nonedivs.length;i++){
			objs.push(nonedivs[i]);
		}
		var divobjs = $$$("div");
		for(var i=0;i<divobjs.length;i++){
			if(divobjs[i].getAttribute("name") == objname){
				objs.push(divobjs[i]);
			}
		}
		return objs;
	}else{
		return document.getElementsByName(objname);
	}
}
function $$$(tagname){
	return document.getElementsByTagName(tagname);
}