redux-typed-action

Typesafely create actions and reducers for Redux in TypeScript.
Using this library possibly makes modules Ducks-like.

Install

npm install redux-typed-action --save

Usage

Create action creators and a reducer using createAction and createReducer provided by redux-typed-action.

import { createAction, createReducer } from 'redux-typed-action'

export type CounterState = number

export const counterActions = {
  add: createAction<CounterState, number>('ADD', (state, payload) => state + payload),
  increment: createAction<CounterState>('INCREMENT', state => state + 1),
  decrement: createAction<CounterState>('DECREMENT', state => state - 1),
}

export default createReducer(counterActions, 0)

console.log(counterActions.increment()) // { type: 'INCREMENT' }
console.log(counterActions.add(100))    // { type: 'ADD', payload: 100 }
// counterActions.increment(100)        // compile error: payload of increment() requires undefined
// counterActions.add('100')            // compile error: payload of add() requires number

And use them normally with combineReducers, createStore, bindActionCreators of Redux.

import { bindActionCreators, combineReducers, createStore } from 'redux'
import counterReducer, { CounterState, counterActions } from './modules/counter'  // import the above

export interface State {
  counter: CounterState
  // ...some other states
}

export const store = createStore<State>(combineReducers({
  counter: counterReducer,
  // ...some other reducers
}))

const dispatch = store.dispatch.bind(store)

export const actions = {
  counter: bindActionCreators(counterActions, dispatch),
  // ...some other action creators
}

console.log(store.getState())     // { counter: 0 }
actions.counter.increment()
console.log(store.getState())     // { counter: 1 }
actions.counter.add(100)
console.log(store.getState())     // { counter: 101 }

// actions.counter.increment(100) // compile error: payload of increment() requires undefined
// actions.counter.add('100')     // compile error: payload of add() requires number

Why?

Using Redux requires some boilerplate code. In TypeScript, redundant code increases.
The reducer have to identify the type of the action by the type property. Therefore, each action should be typed explicitly and that type will be shared with the action creator and the reducer.

// cf. https://stackoverflow.com/questions/35482241/how-to-type-redux-actions-and-redux-reducers-in-typescript
const INCREMENT = 'INCREMENT'
const DECREMENT = 'DECREMENT'
const ADD = 'ADD'

interface IncrementAction {
  type: typeof INCREMENT
}
interface DecrementAction {
  type: typeof DECREMENT
}
interface AddAction {
  type: typeof ADD
  payload: number
}

type Action = IncrementAction | DecrementAction | AddAction

const increment: () => IncrementAction = () => ({ type: INCREMENT })
const decrement: () => DecrementAction = () => ({ type: DECREMENT })
const add: (payload: number) => AddAction = payload => ({ type: ADD, payload })

const reducer = (state: number, action: Action) => {
  switch (action.type) {
    case INCREMENT:
      return state + 1
    case DECREMENT:
      return state - 1
    case ADD:
      return state + action.payload
    default:
      return state
  }
}

But it is painful to define type for each action.

This library offers you to declare type of payload as an inline type literal and use that payload immediately once.

const someAction = createAction<State, { prop1: Prop1, prop2?: Prop2 }>('SOME_ACTION', (state, { prop1, prop2 }) => ({ ...state, prop1, prop2 }))

The created action creator requires a parameter of the type declared above. The compiler and IDE will help you. I think this way is safe, efficient and easy to maintain.

API

createAction<State, Payload, Metadata>(type: string, handler: (State, Payload, Metadata) => State, metadataFactory: Payload => Metadata) => ActionCreator<State, Payload, Metadata>

Returns a new action creator.

createReducer<State>(actions: Record<string, ActionCreator<State, any, any>>, initialState: State) => Reducer<State>

Returns a new reducer.