React reducers keyed by action type

auto-reducers.js

const reducers = {}

// these could be easily split up across different files
reducers.FETCH_RESULT = (state, result) => Object.assign({}, { myData: result.myData }, state }
reducers.ADD_ITEM = (state, item) => Object.assign({}, { items: state.items.concat(item) }, state }
reducers.REMOVE_ITEM = (state, item) => Object.assign({}, { items: ... }, state }

// the main reducer
reducer = (state, action) => {
  return reducers[action.type](state, action.data)
}