document.write asynchronous (JavaScript)

Question

I've got some tracking code that I have to embed in the footer of my page. The tracking code is from a 3rd party company and uses document.write which of course is blocking. I've sent a support request to the company and they don't seem to have any interest in changing the code.

The tracking code looks something like this:

document.write (
  '<img src="http://company-url.com/visitor.gif?ts='+
  new Date().getTime()+
  '&ref='+escape(document.referrer) + '">'
);

So, my question is, is it possible to make document.write non blocking?

What do you mean it is blocking? Can you not just rewrite it to be document.getElementById('footer').innerHTML = '<img ... />'? — putvande
– putvande, Commented Dec 9, 2013 at 16:51
I wouldn't use document.write at all if I had the choice! — MackieeE
– MackieeE, Commented Dec 9, 2013 at 16:51
So you know, it's not document.write that's blocking, but rather all script execution is blocking, unless you use stuff like defer or async. But then document.write doesn't work any longer. — Jacob
– Jacob, Commented Dec 9, 2013 at 16:52
Is this third-party code an inline script or one with an external src? If the latter, there's not much you can do, but if it's inline so you can change it, @bfavaretto's solution would work. — Jacob
– Jacob, Commented Dec 9, 2013 at 16:58

bfavaretto · Accepted Answer · 2013-12-09 16:52:28Z

1

No, it's not possible to make document.write asynchronous. But you can just append an img to the body after page load:

window.onload = function() {
    var url = 'http://company-url.com/visitor.gif?ts='+new Date().getTime()+'&ref='+escape(document.referrer);
    var img = document.createElement('img');
    img.src = url;
    document.body.appendChild(img);
};

answered Dec 9, 2013 at 16:52

bfavaretto

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