code: function isSpecialKey( key ) {
  		return (
  			( key <= 47 &&
  				key !== VK.SPACEBAR &&
  				key !== VK.ENTER &&
  				key !== VK.DELETE &&
  				key !== VK.BACKSPACE &&
  				( key < 37 || key > 40 ) ) ||
  			key >= 224 || // OEM or non-printable
  			( key >= 144 && key <= 150 ) || // Num Lock, Scroll Lock, OEM
  			( key >= 91 && key <= 93 ) || // Windows keys
  			( key >= 112 && key <= 135 )
  		); // F keys
  	}
docs: Excludes arrow keys, delete, backspace, enter, space bar. Ref: https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent.keyCode