Affecting Support for window.event and Event.returnValue has been added again

Published: | Categories: DOM


Firefox 65 has re-added the support for the Internet Explorer-derived window.event and Event.prototype.returnValue properties, which was once landed on Firefox 63 but soon disabled on non-Nightly channels due to several site compatibility issues.

In Firefox 65 and later, when the keyCode property of the keypress event is 0, the value will be the same as charCode. Conversely, when charCode is 0, it will be the same as keyCode. Although this mirroring behaviour matches other browsers and is expected to solve most of the compatibility issues, user agent sniffing might cause another issues like the Closure Library, which has already been solved by Google.

Web developers are also discouraged to use these once-non-standard properties for browser detection.

Update: This change has been postponed to Firefox 66 to deal with an input issue in Confluence’s comment editor.