Gotchas with keyboard events

A few days ago I saw several bugs introduced by a well meaning dev who wanted to heed the UIEvent.which deprecation announcement and use the .key property instead. But even if .which is deprecated - that's actually untrue for every browser out there at the moment - the implementation of replacement properties is not fully supported. First, there is the complication of the effect of the Shift key on the .key property. If you press Shift+3, then .which will be '3' and .key will be '#' and, for Shift-A, 'a' and 'A'. And that happens on a standard United States keyboard layout. For other layouts it's different. There is the concept of a Dead key, which you press on some keyboards to get a character with the press of another key, like adding an accent. In that case the .key property reads 'Dead'! Second, the .key property is not always there. For example the Edge (and probably Chrome) code to autofill fields is simulating typing (with isTrusted true) without specifying a key. This may not…