/*
	Class name : webAjax
	Example    :
	var url="file.html";
	var pars="id="+ value;
	var myajax = new webAjax(fun);
	myajax.get(url,pars);//myajax.get(url,pars) or myajax.post(url,pars);
*/
function webAjax(fun){//fun 为异步回调函数
	var aObj = new Object();
	aObj.xmlhttp = null;
	aObj.backFun = fun;

	//初始化xmlhttp
	aObj.InitAjax = function() {
		var getObj = false;
		if(window.XMLHttpRequest){//IE7, Mozilla ,Firefox 等浏览器内置该对象
			getObj = new XMLHttpRequest();
		}else if(window.ActiveXObject){//IE6、IE5
			try { getObj = new ActiveXObject("Msxml2.XMLHTTP");} catch (e) { }
			if (getObj == null) try { getObj = new ActiveXObject("Microsoft.XMLHTTP");} catch (e) { }
		}else{
			alert('你的浏览器不支持该对象.');	
		}
		return getObj;
	}
	aObj.xmlhttp = aObj.InitAjax();
	
	//设置异步回调函数
	aObj.handleStateChange = function() {
	  if(aObj.xmlhttp.readyState==4 && aObj.xmlhttp.status == 200) {
	   aObj.backFun(aObj.xmlhttp);
	  }
	}
	
	//get发送
	aObj.get = function(url,pars) {
	  aObj.xmlhttp.onreadystatechange = aObj.handleStateChange;
	  aObj.xmlhttp.open("GET",url + "?" + pars,true);
	  aObj.xmlhttp.send(null);
	}
	
	//post发送
	aObj.post = function(url,pars) {
	  aObj.xmlhttp.onreadystatechange = aObj.handleStateChange;
	  aObj.xmlhttp.open("POST",url,true);
	  aObj.xmlhttp.setRequestHeader("cache-control","no-cache");
	  aObj.xmlhttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
	  aObj.xmlhttp.send(pars);
	}
	
	return aObj;
}