dynamically created iframe triggers onload event twice

Question

I created an iframe dynamically and found that this iframe trigger onload event twice.

var i=0;
frameOnload=function(){
  console.log(i++);  
};

var ifr=doc         


        

Answer 1

FWIW, while I was able to reproduce double onload in case where iframe.src is javascript:, I was not able to reproduce it with a normal HTTP URL (onload was happening once). However, when you change the order of calls so that iframe.src is set after appending to body, then the double-load happens (again, webkit only):

var i = 0;

var iframe = document.createElement("iframe");
iframe.onload = function(){
  console.log("frameOnload", ++i);
};
document.body.appendChild(iframe);
iframe.src = "http://www.example.org/";
//iframe.src = "http://www.example.org/404";

// double onload!

When I assign src before appending, I get one onload call.

var i = 0;

var iframe = document.createElement("iframe");
iframe.onload = function(){
  console.log("frameOnload", ++i);
};
iframe.src = "http://www.example.org/";
//iframe.src = "http://www.example.org/404";
document.body.appendChild(iframe);

// only one onload