关于iframe绑定onload事件

var iframe=document.getElementById('center');
if(!iframe) return false;
if (iframe.attachEvent){
iframe.attachEvent("onload", function(){

});
iframe.onreadystatechange=function(){
if(this.readyState=="complete"){
--------------操作---------------
}
};
} else {
iframe.onload = function(){
---------------操作----------------------
};
}