第三方像素，无错误或延迟

Question

I have a database of 3rd party tracking pixels that I add to my own output to either inform that third party of an event or let them set their cookie. Easiest to handle are image pixels - you just set up <img src="..."> and everything just works. However, some pixels in database are of script type - ie 3rd party server returns empty string and Content-Type as text/javascript .

So far I thought of following approaches:

1. Just insert them in same img . Request will succeed, but there will be warning on console and some users just don't like that
2. Give those pixels proper <script> tag while writing it with document.write - depending on browser, slow response of 3rd party server might cause entire page to halt, and that is also very bad.
3. Dynamically generate DOM script element with necessary src and append it somewhere in head . Seems to work, but I didn't test extensively yet and not sure if there's any hidden problems I'm missing.

So, is there some generally accepted method to include such pixels in a way that would guarantee no errors in console or halts on slow 3rd party server response? (additional points if it can handle some other arbitrary content type, not just text/javascript ).

Answer 1

There's an async attribute which IE ignores, yet makes your scripts load asynchronously in other browsers, thereby not blocking site download.

http://davidwalsh.name/html5-async

On how to insert it well (and perhaps that also works in IE, look at comments): https://plus.google.com/116910304844117268718/posts/TripyAFKMof