How to detect idle time in JavaScript elegantly?

Question

Is it possible to detect \"idle\" time in JavaScript?
My primary use case probably would be to pre-fetch or preload content.

Idle time:

Answer 1

You could probably detect inactivity on your web page using the mousemove tricks listed, but that won't tell you that the user isn't on another page in another window or tab, or that the user is in Word or Photoshop, or WOW and just isn't looking at your page at this time. Generally I'd just do the prefetch and rely on the client's multi-tasking. If you really need this functionality you do something with an activex control in windows, but it's ugly at best.