documentfullscreenElement

The documentfullscreenElement property in JavaScript is a read-only attribute of the Document interface. It returns the Element that is currently in full-screen mode for the document, or null if no element is in full-screen mode.

This property is part of the Fullscreen API, which allows web applications to request that the browser display specific elements in full-screen mode, typically for an immersive user experience such as watching videos or playing games. When an element enters full-screen mode, it effectively covers the entire screen, obscuring other content.

The value of documentfullscreenElement changes dynamically. If an element has requested full-screen mode and the browser grants it, that element will be assigned to documentfullscreenElement. When the element exits full-screen mode, either programmatically or by user action, documentfullscreenElement will be set back to null.

Developers can use this property to check the current full-screen status and make decisions about how their application should behave. For instance, a video player might display different controls or adjust its layout based on whether it is in full-screen mode. It is a crucial part of managing and responding to the full-screen state within a web page.