onkeydown and onkeyup events don't work on Internet Explorer 8

Question

My code works without problems on IE9/IE10, FF, Chrome and opera but on older Internet Explorer no Keyboard input is handled.

I have the following code for handling events. It should only fire when a new button is pressed.

lastEvent = void 0;

heldKeys = {};

window.onkeydown = function(event) {
if (lastEvent && lastEvent.keyCode === event.keyCode) {
  return;
}
lastEvent = event;
heldKeys[event.keyCode] = true;
switch (event.which) {
  case 80:
    return myamp.userInput("positiv");
  case 81:
    return myamp.userInput("negativ");
}
};

window.onkeyup = function(event) {
  lastEvent = null;
  return delete heldKeys[event.keyCode];
};

Answer 1

Try

lastEvent = void 0;

heldKeys = {};

window.onkeydown = function(event) {
    event = event || window.event; //IE does not pass the event object
    if (lastEvent && lastEvent.keyCode === event.keyCode) {
        return;
    }
    lastEvent = event;
    heldKeys[event.keyCode] = true;

    var keyCode = event.which || event.keyCode; //key property also different

    switch (keyCode) {
        case 80:
            return myamp.userInput("positiv");
        case 81:
            return myamp.userInput("negativ");
    }
};

window.onkeyup = function(event) {
    event = event || window.event;
    lastEvent = null;
    return delete heldKeys[event.keyCode];
};