Detect Fn key with js

Question

Hello I was wondering if it is possible to catch the fn key with js.

What i'm trying to achieve is detect the fn + f7 keypress.

Here is my code which is not triggered with the fn key :

document.addEventListener("keydown", onKeyDown, false);

function onKeyDown(e) {
  console.log(e);
}

Update : I found that detecting fn + f5 works on windows but not for my linux. Is there a package to install to add media keys for firefox?

Answer 1

Most FN keys are implemented in firmware and won't be recognized by applications. You can use a website like this one to test out what javascript can handle:

http://keycode.info/

Answer 2

You can't catch when fn key was pressed.

However if you press fn+F7 it would generate different event object than if you press solely F7 - considering that there is function bound to that key. So in my case I do not have anything bound on F7, therefore there will be no event generated if I press fn+F7 keys.

If I press F3 and then fn+F3, following codes will be generated:

KeyboardEvent {isTrusted: true, key: "F3", code: "F3", location: 0, ctrlKey: false, …}
KeyboardEvent {isTrusted: true, key: "AudioVolumeUp", code: "AudioVolumeUp", location: 0, ctrlKey: false, …}

Hope this helps.

----More info below----

As I expected fn key does not really generate any keycode. Instead, on the hardware level, when pressed in combination with some other keys it is generating unique keycode.

Information based on answer from this question: https://askubuntu.com/questions/827925/remapping-the-fn-key

And this: https://askubuntu.com/questions/270416/how-do-fn-keys-work