actions.js

const lightenPad = createAction(LIGHTEN_PAD);
const lightenOffPad = createAction(LIGHTEN_OFF_PAD);

lightenPad({ id: 'green' }); // { type: 'LIGHTEN_PAD', payload: { id: 'green' } };
lightenOffPad(); // { type: 'LIGHTEN_OFF_PAD', payload: {} };

function pads(state, action) {
  const { type, payload } = action;
  switch(type) {
    case LIGHTEN_PAD:
      return state.map(b => ({
        ...b,
        active: payload.id === b.id,
      }));

    case LIGHTEN_OFF_PAD:
      return state.map(b => ({
        ...b,
        active: false,
      }));

    default:
      return state;
  }
}