My own personal preference for building reducers for Redux.

var makeReducer = require('create-redux-reducer-from-map')

const arithmeticReducer = makeReducer({
	ADD: (state, action) => state + action.payload,
	SUBTRACT: (state, action) => state - action.payload
}, 0)

makeReducer(mapOfFunctions[, initialState])

Returns a reducer appropriate for Redux. Takes an map of action types to functions taking (state, action).

License

WTFPL