HTMLDialogElement.showModal()

The showModal() method of the HTMLDialogElement interface displays the dialog as a modal dialog, over the top of any other dialogs or elements that might be visible.

A modal dialog displays in the top layer, along with a ::backdrop pseudo-element. Elements inside the same document as the dialog, except the dialog and its descendants, become inert (as if the inert attribute is specified). Only the containing document becomes blocked; if the dialog is rendered inside an iframe, the rest of the page remains interactive.

Exceptions: InvalidStateError DOMException Thrown if the dialog is already open and non-modal (i.e., if the dialog has already been opened with HTMLDialogElement.show()).