Does Gmail Use Setinterval() Or Settimeout() To Do Periodical Refresh?

I guess they use these two functions to make an Ajax call to their server but I am not sure. How do they do that? Thank you.

Solution 1:

I haven't tried to reverse-engineer Gmail, but most likely they are using some form of Comet (reverse AJAX).

With this approach information is available instantly without any delay and additional network traffic.