code: function modifierStateGetter(keyArg) {
    var syntheticEvent = this;
    var nativeEvent = syntheticEvent.nativeEvent;
    if (nativeEvent.getModifierState) {
      return nativeEvent.getModifierState(keyArg);
    }
    var keyProp = modifierKeyToProp[keyArg];
    return keyProp ? !!nativeEvent[keyProp] : false;
  }
docs: IE8 does not implement getModifierState so we simply map it to the only modifier keys exposed by the event itself, does not support Lock-keys. Currently, all major browsers except Chrome seems to support Lock-keys.