works on chrome, not on firefox ( event is not defined )

redux-dock-handlekey.js

handleKeyDown(e) {
    if (!e.ctrlKey) {
      return;
    }
    e.preventDefault();

    const key = event.keyCode || event.which;
    const char = String.fromCharCode(key);
    switch (char.toUpperCase()) {
    case this.props.toggleVisibilityKey.toUpperCase():
      this.props.dispatch(toggleVisibility());
      break;
    case this.props.changePositionKey.toUpperCase():
      this.props.dispatch(changePosition());
      break;
    default:
      break;
    }
  }