Something bugging me about Facebook Timer

If you have used Facebook, you might have the noticed there is a timer in everything that appear开发者_运维百科s on the page, which are constantly updating in minutes. Which, I am wondering is not affecting the performance of the website.

Whether It is a Ajax Request triggered by a timer or Just plain client side Timer, the point is a lot of timers are used. Wont using a lot timers like this affect the site's performance? or There is something I am missing.

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It only takes one timer to do what Facebook is doing. Each time it fires, it iterates over all abbr elements with class="timestamp and calculates an update based on the custom data-date attribute they've defined.

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Sure, anything you add that runs a setInterval() will change the performance of a website.

However, unless Facebook shows time down to the second, it probably runs once a minute.

I've also noticed Facebook uses lot of fuzzy times, like just then, etc. This may mean the setInterval() runs on an even longer interval.