...Its main purpose is to let web applications adapt behavior depending on whether the page is actually being viewed — for example, pausing animations, postponing heavy computations, or stopping unnecessary network requests when the user switches to another tab. The library hides browser vendor-prefixes and normalizes visibility events so you don’t have to manage cross-browser quirks yourself. On top of simple visibility detection, Visibility.js adds useful helpers such as a timer function that only runs when the page is visible. ...