JS onload 时实现多个函数队列执行

function firstFuntion(){
        console.log("我是first啊");
    }
   function secondFuntion(){
        console.log("我是second啊");
    }
   function addLoadEvent(func){
       var oldonload = window.onload;
       if(typeof window.onload != 'function'){
           window.onload = func;
       }else{
           window.onload = function(){
               oldonload();
               func();
               console.log("队列成功了");
           }
       }
   }
    addLoadEvent(firstFuntion);
    addLoadEvent(secondFuntion);