code: function listenersById(state = {}, { type, path, payload }) {
    switch (type) {
      case actionTypes.SET_LISTENER:
        return {
          ...state,
          [payload.name]: {
            name: payload.name,
            path,
          },
        };
      case actionTypes.UNSET_LISTENER:
        return omit(state, [payload.name]);
      default:
        return state;
    }
  }
docs: Reducer for listeners ids. Changed by `SET_LISTENER` and `UNSET_LISTENER`
  actions.
  @param  {Object} [state={}] - Current listenersById redux state
  @param  {Object} action - Object containing the action that was dispatched
  @param  {String} action.type - Type of action that was dispatched
  @return {Object} listenersById state after reduction (used in listeners)
  @private