Executing JavaScript code will definitely involve the processor cache and a high-resolution timer is accessible via browser performance API.

Chrome JavaScript timer throttling: Google's tests show it saves up to 2 hours' battery life Chrome will soon throttle JavaScript timers in the background, so the browser uses significantly less ...

Google is testing changes to the JavaScript timers for background tabs in Chrome that improve battery usage by 13% to 28%. Users can enable the feature in the Canary version of Chrome and Edge.