CloseWatcher: cancel event

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

A cancel event is fired at a CloseWatcher object before the close event, so that close can be prevented from firing, if necessary. It is triggered by all close signals (e.g. the Esc key) as well as CloseWatcher.requestClose().

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

js
addEventListener("cancel", (event) => { })

oncancel = (event) => { }

Event type

An Event.

Examples

Using the cancel event

In this example, we ask the user to confirm that they really want to close the component, and if they don't, we cancel the event using Event.preventDefault(), which prevents the close event from being fired.

js
watcher.addEventListener("cancel", (e) => {
  if (e.cancelable && hasUnsavedData) {
    const userReallyWantsToClose = confirm("Are you sure you want to close?");
    if (!userReallyWantsToClose) {
      e.preventDefault();
    }
  }
};

// Trigger a close request manually
watcher.requestClose();

Specifications

Specification
HTML
# handler-closewatcher-oncancel

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
cancel event
Experimental

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support
Experimental. Expect behavior to change in the future.
User must explicitly enable this feature.