event.keyCode is deprecated, should upgrade to event.code

[Meng Weng Wong]

https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyCode states

You should avoid using this if possible; it's been deprecated for some time. Instead, you should use KeyboardEvent.code, if it's implemented. Unfortunately, some browsers still don't have it, so you'll have to be careful to make sure you use one which is supported on all target browsers.

event.keyCode shows up in places like

impress.js/src/plugins/navigation/navigation.js

Lines 95 to 107 in 9475720

 switch ( event.keyCode ) { 
     case 33: // Pg up 
     case 37: // Left 
     case 38: // Up 
              api.prev( event ); 
              break; 
     case 9:  // Tab 
     case 32: // Space 
     case 34: // Pg down 
     case 39: // Right 
     case 40: // Down 
              api.next( event ); 
              break; 

Unless there are any objections I will fork and work toward a PR to fix this.

[Janis Hutz]

That's good

[Janis Hutz]

What I expected to be a problem with this solution: https://caniuse.com/?search=keyboardevent.code

This will break impress.js in older browsers like IE and mobile browsers (aka. Safari for iOS, Firefox for Android, etc.)

Compare it to: https://caniuse.com/?search=keyboardevent.keyCode, which is supported by almost every major browser out there.

We should consider implementing a way to notify the user about incompatible plugins & automatically disable the plugins relying on these features, if the browser does not support it to retain support for old browsers with the most recent versions of impress.js.

Although this is great to offer, I personally am in favour of dropping support for the old browsers barely anyone uses any more nowadays. People that need to use those browsers should use a different CDN-Link or V2.0.0 instead of a new (future) release or upstream.

[Meng Weng Wong]

Let's move the discussion into the PR #851