According to MDN, keyCode (https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyCode) and which (https://developer.mozilla.org/en-US/docs/Web/API/UIEvent/which) are both deprecated, though it doesn't look like any browsers have dropped support for them yet. We should look into adding a more current option to ensure future support. KeyBoardEvent.key maybe? https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key I defer to the folks who know more about front-end web design than me though. :) These come up at least in shortcut.js...not sure where else they may be used.
*** Bug 22281 has been marked as a duplicate of this bug. ***