function loadExtentFile(filename, fileType){
	var b = document.scripts[document.scripts.length-1].src.match(/[\s\S]*\//)[0];
    if(fileType == "js"){
        var oJs = document.createElement('script');        
        oJs.setAttribute("type","text/javascript");
        oJs.setAttribute("src", filename);//文件的地址 ,可为绝对及相对路径
        document.getElementsByTagName("head")[0].appendChild(oJs);//绑定
    }else if(fileType == "css"){
        var oCss = document.createElement("link"); 
        oCss.setAttribute("rel", "stylesheet"); 
        oCss.setAttribute("type", "text/css");  
        oCss.setAttribute("href", b+"/"+filename);
        document.getElementsByTagName("head")[0].appendChild(oCss);//绑定
    }
}
loadExtentFile("need/loadding.css", "css");


var open = window.XMLHttpRequest.prototype.open,
send = window.XMLHttpRequest.prototype.send,
onReadyStateChange;

function openReplacement(method, url, async, user, password) {
	console.log("开始请求")
	$("body").append('<div id="over" class="over"></div>');
	$("body").append('<div id="layout" class="layout"><img src="../images/o_31.gif" /></div>')
	document.getElementById("over").style.display = "block";
    document.getElementById("layout").style.display = "block";
var syncMode = async !== false ? 'async' : 'sync';
return open.apply(this, arguments);//可以理解成是继承，继承open对象中的属性和方法
}

function sendReplacement(data) {

if(this.onreadystatechange) {
    this._onreadystatechange = this.onreadystatechange;
}
this.onreadystatechange = onReadyStateChangeReplacement;

return send.apply(this, arguments);
}

function onReadyStateChangeReplacement() {

//如果不判断readyState等于４,state只要变化，就进了if内，会导致一个ajax call，多次打印
if(this._onreadystatechange&&this.readyState==4) {
//我这里是需要对ajax中的json类型进行过滤
        if(this.getResponseHeader("Content-Type")=='application/json'){
            if(this.responseText){
            var obj = eval('('+this.responseText+')');
          //  console.log('NAME'+obj.emptyFlag+"\n");
            }
        }
	$("#over").remove();
	$("#layout").remove();
	console.log("请求结束")
    return this._onreadystatechange.apply(this, arguments);
}

}


//可以打印js对象
function dump_obj(myObject) { 
var s = ""; 
for (var property in myObject) { 
s = s + "\n "+property +": " + myObject[property] ; 
} 
console.log(s); 
}  
window.XMLHttpRequest.prototype.open = openReplacement;
window.XMLHttpRequest.prototype.send = sendReplacement;