As the article explains, there is a difference between the physical keyCode and character it corresponds to. Which to use really depends on what it is being used for, and there are situations for both. The article suggests checking the character typed, but this is not always the correct way to do it.
For instance, the most annoying are games which default to WASD based on the letter typed and not the physical keys (I've seen this both in web app and native games). Using WASD based on letters simply does not make sense because the whole purpose is to mimic arrow keys. If you base it off of letters typed, then on Dvorak it's like if you used ,A;H on Qwerty which makes absolutely no sense for directional navigation.
For shortcuts where the letter has a meaning, then you might want to look at the actual character. But beware that even alphanumeric keys are not always in the same place because of layouts such as Dvorak and Colemak.