前端学习之二_JS公共库（addLoadEvent,insertAfter,getHttpObject）

function addLoadEvent(func){
    var oldOnLoad=window.onload;
    if(typeof window.onload!="function"){
        window.onload=func;
    }else{
        window.onload=function(){
            oldOnLoad();
            func();
        }
    }
}

function insertAfter(newElement,targetElement){
    var parent=targetElement.parentNode;
    if(parent.lastChild==targetElement){
        parent.appendChild(newElement);
    }else{
        parent.insertBefore(newElement,targetElement.nextSibling);
    }
}

//获取ajax中的XMLHttpRequest对象，保证各个浏览器的兼容

function getHttpObject(){
    if(typeof XMLHttpRequest=="undefined"){
        XMLHttpRequest=function(){
            try{
                return new ActiveXObject("Msxml2.XMLHttp.6.0");
            }catch(e){}
            try{
                return new ActiveXObject("Msxml2.XMLHttp.3.0");
            }catch(e){}
            try{
                return new ActiveXObject("Msxml2.XMLHttp");
            }catch(e){}
        return false;
        }
    }
    return new XMLHttpRequest();
}