Question

I read somewhere that setInterval is CPU intensive. I created a script that uses setInterval and monitored the CPU usage but didn’t notice a change. I want to know if there is something I missed.

What the code does is check for changes to the hash in the URL (content after #) every 100 milliseconds and if it has changed, load a page using AJAX. If it has not changed, nothing happens. Would there be any CPU issues with that.

Answer 1

I don’t think setInterval is inherently going to cause you significant performance problems. I suspect the reputation may come from an earlier era, when CPUs were less powerful.

There are ways that you can improve the performance, however, and it’s probably wise to do them:

1. Pass a function to setInterval, rather than a string.
2. Have as few intervals set as possible.
3. Make the interval durations as long as possible.
4. Have the code running each time as short and simple as possible.

Don’t optimise prematurely — don’t make life difficult for yourself when there isn’t a problem.

One thing, however, that you can do in your particular case is to use the onhashchange event, rather than timeouts, in browsers that support it.