JavaScript

Take Control of Keyboard: KeyPress & KeyDown

Lets see some fact tables:

Key: a keyDown keyPress
e.which 65 65
e.charCode 0 65
e.keyCode 65 0

And String.fromCharCode(65) is “a”, so correct. However when it comes to upper cases:

Key: A keyDown keyPress
e.which 65 97
e.charCode 0 97
e.keyCode 65 0

So to detect a “A”, keyDown can only detect a “shift” and an “a”. We need to rely on keyPress here.

However for control keys, keyPress doesn’t work that well.

Key: ESC keyDown keyPress
e.which 27 0
e.charCode 0 0
e.keyCode 27 27

 

Key: ESC keyDown keyPress
e.which 16 Undetectable
e.charCode 0 Undetectable
e.keyCode 16 Undetectable

So all in all:

  • Use event.which with String.fromCharCode(num);
  • Use keyDown for Controls, keyPress for Character detection.

Also, pay attention to the detection of BackSpace. UseĀ e.preventDefault(); to prevent Firefox from navigating back.

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