Page visibilityThe document.visibilityState and document.hidden properties tell you whether the page is visible to the user (for example, it's not minimized or in a background tab).widely2015-07-292018-01-29https://html.spec.whatwg.org/multipage/interaction.html#page-visibilitypagevisibilityhttps://developer.mozilla.org/docs/Web/API/Document/hiddenapi.Document.hiddenapi.Document.visibilityStateapi.Document.visibilitychange_eventhttps://nowyoucanuse.com/features--page-visibility.html