HTMLElement: inert property

The HTMLElement property inert reflects the value of the element's inert attribute. It is a boolean value that, when present, makes the browser "ignore" user input events for the element, including focus events and events from assistive technologies. The browser may also ignore page search and text selection in the element. This can be useful when building UIs such as modals where you would want to "trap" the focus inside the modal when it's visible.

Note that if the inert attribute is unspecified, the element itself may still inherit inertness from its parent. However, that inherited inertness is not reflected by this property's value.