How can I tell if an event comes from right Ctrl key?

Question

I have an event listener in Javascript, I can tell whether a key event is Ctrl (e.keyCode == 17), but how can I know this Ctrl comes from the right one or left one?

Yeorgi

You can't. I'm sorry. I feel your pain. – Munshi

Answer 1

I don't think the keyCode is different.

You can use e.ctrlKey for a better way to determine if the control key was pressed.

It seems Flash can not tell which one is pressed either (either that or coded incorrectly).

Touchy

They are abstracted. E.g. I can choose a ton of different options for each of them in my Ubuntu Keyboard settings. – Wedurn

You can definitely write software that differentiates between the two on a low level, so no, it can't be abstracted on the hardware level. It's probably abstracted on the OS level, though. – Chattanooga

MSIE can differentiate the left and right Ctrl key, see my answer on that point. – Mayenne

Answer 2

Just a quick note: I wouldn't base an architecture / design on the availability of the right control key - many laptop keyboards may not have two control keys.

Frolicsome

Answer 3

MSIE provides a ctrlLeftproperty on most events. The property values are:

• true if the left key was pressed during the event
• false if the left key was not pressed.

You can combine event.ctrlKey and event.ctrlLeft to determine if the right Ctrl key was pressed:

if (event.ctrlKey) {
    if (event.ctrlLeft) {
        // left Ctrl key pressed
    } else {
        // right Ctrl key pressed
    }
} else {
    // no Ctrl key pressed
}

Note that the ctrlLeftproperty in a keyup is undefined because the Ctrl key is not pressed anymore.

Tested under MSIE7 and MSIE9. Does not work under Firefox.

See http://help.dottoro.com/ljqlvhuf.php for details.

Mayenne

Not very useful unfortunately if it's IE only. – Touchy

Answer 4

If you traced it you will find the same key is used for both (17) .. I think it is not possible to differentiate

Plainsong

Answer 5

I don't know if it was available when this was asked, but you can distinguish left- from right-ctrl, as well as alt and shift. You can now use the KeyboardEvent.DOM_KEY_LOCATION_* properties to make this distinction.

See Can javascript tell the difference between left and right shift key?

Be aware though, I discovered that Chrome appears to have a defect in its implementation. See How can I distinguish left- and right- shift, ctrl, and alt keys onkeyup in Chrome with Javascript

Qua

Answer 6

There is event.location property for left ctrl key it will be 1 for right one 2, you can check browser support on canIuse

if (e.which == 17) {
   if (event.location == 1) {
      // left ctrl key
   } else if (event.location == 2) {
      // right ctrl key
   }
}

Magnetics