完美判断iframe是否加载完成

var iframe = document.createElement("iframe");
iframe.style.width = "265px";
iframe.style.height = "490px";
iframe.style.border = "none";
iframe.src = "http://cnblogs.com/walls";
        
if(iframe.attachEvent){
     //IE
     iframe.attachEvent("onload", function(){
         alert("loaded 1");
     });
}else{
     iframe.onload = function(){
         console.log("loaded 2");
     };
}