dialog-polyfill.js is a polyfill for dialog and form method="dialog". Dialog is an element for a popup box in a web page, including a modal option that will make the rest of the page inert during use. This could be useful to block a user's interaction until they give you a response, or to confirm an action. See the HTML spec. This polyfill works on modern versions of all major browsers. It also supports IE9 and above.