Is setInterval CPU intensive?

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

Answer 1

There's a bit of marketing going there under the "CPU intensive" term. What it really means is "more CPU intensive than some alternatives". It's not "CPU intensive" as in "uses a whole lot of CPU power like a game or a compression algorithm would do".

Explanation :

Once the browser has yielded control it relies on an interrupt from the underlying operating system and hardware to receive control and issue the JavaScript callback. Having longer durations between these interrupts allows hardware to enter low power states which significantly decreases power consumption. By default the Microsoft Windows operating system and Intel based processors use 15.6ms resolutions for these interrupts (64 interrupts per second). This allows Intel based processors to enter their lowest power state. For this reason web developers have traditionally only been able to achieve 64 callbacks per second when using setTimeout(0) when using HTML4 browsers including earlier editions of Internet Explorer and Mozilla Firefox.

Over the last two years browsers have attempted to increase the number of callbacks per second that JavaScript developers can receive through the setTimeout and setInterval API’s by changing the power conscious Windows system settings and preventing hardware from entering low power states. The HTML5 specification has gone to the extreme of recommending 250 callbacks per second. This high frequency can result in a 40% increase in power consumption, impacting battery life, operating expenses, and the environment. In addition, this approach does not address the core performance problem of improving CPU efficiency and scheduling.

From http://ie.microsoft.com/testdrive/Performance/setImmediateSorting/Default.html