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
No, setInterval is not CPU intensive in and of itself. If you have a lot of intervals running on very short cycles (or a very complex operation running on a moderately long interval), then that can easily become CPU intensive, depending upon exactly what your intervals are doing and how frequently they are doing it.
I wouldn't expect to see any issues with checking the URL every 100 milliseconds on an interval, though personally I would increase the interval to 250 milliseconds, just because I don't expect that the difference between the two would be noticeable to a typical user and because I generally try to use the longest timeout intervals that I think I can get away with, particularly for things that are expected to result in a no-op most of the time.