To help you get started, we've collected the most common ways that typesafe-actions is being used within popular public projects.

Features

• Easily create completely typesafe Actions or even Async Actions
• No boilerplate and completely typesafe Reducers
• Game-changing Helper Types for Redux

Playgrounds & Examples

• Todo-App playground: Codesandbox
• React, Redux, TypeScript - RealWorld App: Github | Demo

Goals

• Secure and Minimal - no third-party dependencies, according to size-snapshot (Minified: 3.48 KB, Gzipped: 1.03 KB), check also on bundlephobia
• Optimized - distribution packages bundled in 3 different formats (cjs, esm and umd) with separate bundles for dev & prod (same as react)
• Quality - complete test-suite for an entire API surface containing regular runtime tests and extra type-tests to guarantee type soundness and to prevent regressions in the future TypeScript versions
• Performance - integrated performance benchmarks to guarantee that the computational complexity of types are in check and there are no slow-downs when your application grow npm run benchmark:XXX

---

Table of Contents

• Installation
• Tutorial v4 (v5 is WIP #188)
  • Constants
  • Actions
    • 1. Basic actions
    • 2. FSA compliant actions
    • 3. Custom actions (non-standard use-cases)
  • Action Helpers
    • Using action-creators instances instead of type-constants
    • Using regular type-constants
  • Reducers
    • Extending internal types to enable type-free syntax with createReducer
    • Using createReducer API with type-free syntax
    • Alternative usage with regular switch reducer
  • Async-Flows
    • With redux-observable epics
    • With redux-saga sagas
• API Docs v4 (v5 is WIP #189)
  • Action-Creators API
    • action
    • createAction
    • createStandardAction
    • createCustomAction
    • createAsyncAction
  • Reducer-Creators API
    • createReducer
  • Action-Helpers API
    • getType
    • isActionOf
    • isOfType
  • Type-Helpers API
    • ActionType
    • StateType
• Migration Guides
  • v4.x.x to v5.x.x
  • v3.x.x to v4.x.x
  • v2.x.x to v3.x.x
  • v1.x.x to v2.x.x
  • Migrating from redux-actions to typesafe-actions
• Compatibility Notes
• Recipes
  • Restrict Meta type in action creator
• Compare to others
  • redux-actions
• Motivation
• Contributing
• Funding Issues
• License

---

Installation

# NPM
npm install typesafe-actions

# YARN
yarn add typesafe-actions

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---

Tutorial v4 (v5 is WIP #188)

To showcase the flexibility and the power of the type-safety provided by this library, let's build the most common parts of a typical todo-app using a Redux architecture:

> WARNING
> Please make sure that you are familiar with the following concepts of programming languages to be able to follow along: Type Inference, Control flow analysis, Tagged union types, Generics and Advanced Types.

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Constants

> RECOMMENDATION:
> When using typesafe-actions in your project you won't need to export and reuse string constants. It's because action-creators created by this library have static property with action type that you can easily access using actions-helpers and then use it in reducers, epics, sagas, and basically any other place. This will simplify your codebase and remove some boilerplate code associated with the usage of string constants. Check our /codesandbox application to learn some best-practices to create such codebase.

Limitations of TypeScript when working with string constants - when using string constants as action type property, please make sure to use simple string literal assignment with const. This limitation is coming from the type-system, because all the dynamic string operations (e.g. string concatenation, template strings and also object used as a map) will widen the literal type to its super-type, string. As a result this will break contextual typing for action object in reducer cases.

// Example file: './constants.ts'

// WARNING: Incorrect usage
export const ADD = prefix + 'ADD'; // => string
export const ADD = `${prefix}/ADD`; // => string
export default {
   ADD: '@prefix/ADD', // => string
}

// Correct usage
export const ADD = '@prefix/ADD'; // => '@prefix/ADD'
export const TOGGLE = '@prefix/TOGGLE'; // => '@prefix/TOGGLE'
export default ({
  ADD: '@prefix/ADD', // => '@prefix/ADD'
} as const) // working in TS v3.4 and above => https://github.com/Microsoft/TypeScript/pull/29510

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Actions

Different projects have different needs, and conventions vary across teams, and this is why typesafe-actions was designed with flexibility in mind. It provides three different major styles so you can choose whichever would be the best fit for your team.

1. Basic actions

action and createAction are creators that can create actions with predefined properties ({ type, payload, meta }). This make them concise but also opinionated.

Important property is that resulting action-creator will have a variadic number of arguments and preserve their semantic names (id, title, amount, etc...).

This two creators are very similar and the only real difference is that action WILL NOT WORK with action-helpers.

import { action, createAction } from 'typesafe-actions';

export const add = (title: string) => action('todos/ADD', { id: cuid(), title, completed: false });
// add: (title: string) => { type: "todos/ADD"; payload: { id: string, title: string, completed: boolean; }; }

export const add = createAction('todos/ADD', action => {
  // Note: "action" callback does not need "type" parameter
  return (title: string) => action({ id: cuid(), title, completed: false });
});
// add: (title: string) => { type: "todos/ADD"; payload: { id: string, title: string, completed: boolean; }; }

2. FSA compliant actions

This style is aligned with Flux Standard Action, so your action object shape is constrained to ({ type, payload, meta, error }). It is using generic type arguments for meta and payload to simplify creation of type-safe action-creators.

It is important to notice that in the resulting action-creator arguments are also constrained to the predefined: (payload, meta), making it the most opinionated creator.

> TIP: This creator is the most compatible with redux-actions in case you are migrating.

import { createStandardAction } from 'typesafe-actions';

export const toggle = createStandardAction('todos/TOGGLE')();
// toggle: (payload: string) => { type: "todos/TOGGLE"; payload: string; }

export const add = createStandardAction('todos/ADD').map(
  (title: string) => ({
    payload: { id: cuid(), title, completed: false },
  })
);
// add: (payload: string) => { type: "todos/ADD"; payload: { id: string, title: string, completed: boolean; }; }

3. Custom actions (non-standard use-cases)

This approach will give us the most flexibility of all creators, providing a variadic number of named parameters and custom properties on action object to fit all the custom use-cases.

import { createCustomAction } from 'typesafe-actions';

const add = createCustomAction('todos/ADD', type => {
  return (title: string) => ({ type, id: cuid(), title, completed: false });
});
// add: (title: string) => { type: "todos/ADD"; id: string; title: string; completed: boolean; }

> TIP: For more examples please check the API Docs.

> RECOMMENDATION
> Common approach is to create a RootAction in the central point of your redux store - it will represent all possible action types in your application. You can even merge it with third-party action types as shown below to make your model complete.

// types.d.ts
// example of including `react-router` actions in `RootAction`
import { RouterAction, LocationChangeAction } from 'react-router-redux';
import { TodosAction } from '../features/todos';

type ReactRouterAction = RouterAction | LocationChangeAction;

export type RootAction =
  | ReactRouterAction
  | TodosAction;

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Action Helpers

Now I want to show you action-helpers and explain their use-cases. We're going to implement a side-effect responsible for showing a success toast when user adds a new todo.

Important thing to notice is that all these helpers are acting as a type-guard so they'll narrow tagged union type (RootAction) to a specific action type that we want.

Using action-creators instances instead of type-constants

Instead of type-constants we can use action-creators instance to match specific actions in reducers and epics cases. It works by adding a static property on action-creator instance which contains the type string.

The most common one is getType, which is useful for regular reducer switch cases:

  switch (action.type) {
    case getType(todos.add):
      // below action type is narrowed to: { type: "todos/ADD"; payload: Todo; }
      return [...state, action.payload];
    ...

Then we have the isActionOf helper which accept action-creator as first parameter matching actions with corresponding type passed as second parameter (it's a curried function).

// epics.ts
import { isActionOf } from 'typesafe-actions';

import { add } from './actions';

const addTodoToast: Epic = (action$, state$, { toastService }) =>
  action$.pipe(
    filter(isActionOf(add)),
    tap(action => { // here action type is narrowed to: { type: "todos/ADD"; payload: Todo; }
      toastService.success(...);
    })
    ...
    
  // Works with multiple actions! (with type-safety up to 5)
  action$.pipe(
    filter(isActionOf([add, toggle])) // here action type is narrowed to a smaller union:
    // { type: "todos/ADD"; payload: Todo; } | { type: "todos/TOGGLE"; payload: string; }

Using regular type-constants

Alternatively if your team prefers to use regular type-constants you can still do that.

We have an equivalent helper (isOfType) which accept type-constants as parameter providing the same functionality.

// epics.ts
import { isOfType } from 'typesafe-actions';

import { ADD } from './constants';

const addTodoToast: Epic = (action$, state$, { toastService }) =>
  action$.pipe(
    filter(isOfType(ADD)),
    tap(action => { // here action type is narrowed to: { type: "todos/ADD"; payload: Todo; }
    ...
    
  // Works with multiple actions! (with type-safety up to 5)
  action$.pipe(
    filter(isOfType([ADD, TOGGLE])) // here action type is narrowed to a smaller union:
    // { type: "todos/ADD"; payload: Todo; } | { type: "todos/TOGGLE"; payload: string; }

> TIP: you can use action-helpers with other types of conditional statements.

import { isActionOf, isOfType } from 'typesafe-actions';

if (isActionOf(actions.add, action)) {
  // here action is narrowed to: { type: "todos/ADD"; payload: Todo; }
}
// or with type constants
if (isOfType(types.ADD, action)) {
  // here action is narrowed to: { type: "todos/ADD"; payload: Todo; }
}

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Reducers

Extending internal types to enable type-free syntax with createReducer

We can extend internal types of typesafe-actions module with RootAction definition of our application so that you don't need to pass generic type arguments with createReducer API:

// types.d.ts
import { StateType, ActionType } from 'typesafe-actions';

export type RootAction = ActionType;

declare module 'typesafe-actions' {
  interface Types {
    RootAction: RootAction;
  }
}

// now you can use
createReducer(...)
// instead of
createReducer(...)

Using createReducer API with type-free syntax

We can prevent a lot of boilerplate code and type errors using this powerfull and completely typesafe API.

Using handleAction chain API:

// using action-creators
const counterReducer = createReducer(0)
  // state and action type is automatically inferred and return type is validated to be exact type
  .handleAction(add, (state, action) => state + action.payload)
  .handleAction(add, ... // <= error is shown on duplicated or invalid actions
  .handleAction(increment, (state, _) => state + 1)
  .handleAction(... // <= error is shown when all actions are handled
  
  // or handle multiple actions using array
  .handleAction([add, increment], (state, action) =>
    state + (action.type === 'ADD' ? action.payload : 1)
  );

// all the same scenarios are working when using type-constants
const counterReducer = createReducer(0)
  .handleAction('ADD', (state, action) => state + action.payload)
  .handleAction('INCREMENT', (state, _) => state + 1);
  
counterReducer(0, add(4)); // => 4
counterReducer(0, increment()); // => 1

Alternative usage with regular switch reducer

First we need to start by generating a tagged union type of actions (TodosAction). It's very easy to do by using ActionType type-helper.

import { ActionType } from 'typesafe-actions';

import * as todos from './actions';
export type TodosAction = ActionType;

Now we define a regular reducer function by annotating state and action arguments with their respective types (TodosAction for action type).

export default (state: Todo[] = [], action: TodosAction) => {

Now in the switch cases we can use the type property of action to narrowing the union type of TodosAction to an action that is corresponding to that type.

  switch (action.type) {
    case getType(add):
      // below action type is narrowed to: { type: "todos/ADD"; payload: Todo; }
      return [...state, action.payload];
    ...

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Async-Flows

With redux-observable epics

To handle an async-flow of http request lets implement an epic. The epic will call a remote API using an injected todosApi client, which will return a Promise that we'll need to handle by using three different actions that correspond to triggering, success and failure.

To help us simplify the creation process of necessary action-creators, we'll use createAsyncAction function providing us with a nice common interface object { request: ... , success: ... , failure: ... } that will nicely fit with the functional API of RxJS. This will mitigate redux verbosity and greatly reduce the maintenance cost of type annotations for actions and action-creators that would otherwise be written explicitly.

// actions.ts
import { createAsyncAction } from 'typesafe-actions';

const fetchTodosAsync = createAsyncAction(
  'FETCH_TODOS_REQUEST',
  'FETCH_TODOS_SUCCESS',
  'FETCH_TODOS_FAILURE',
  'FETCH_TODOS_CANCEL'
)();

// epics.ts
import { fetchTodosAsync } from './actions';

const fetchTodosFlow: Epic = (action$, state$, { todosApi }) =>
  action$.pipe(
    filter(isActionOf(fetchTodosAsync.request)),
    switchMap(action =>
      from(todosApi.getAll(action.payload)).pipe(
        map(fetchTodosAsync.success),
        catchError((message: string) => of(fetchTodosAsync.failure(message))),
        takeUntil(action$.pipe(filter(isActionOf(fetchTodosAsync.cancel)))),
      )
    );

With redux-saga sagas

With sagas it's not possible to achieve the same degree of type-safety as with epics because of limitations coming from redux-saga API design.

Typescript issues:

• Typescript does not currently infer types resulting from a yield statement so you have to manually assert the type e.g. const response: Todo[] = yield call(...

Here is the latest recommendation although it's not fully optimal. If you managed to cook something better, please open an issue to share your finding with us.

import { createAsyncAction, createReducer } from 'typesafe-actions';
import { put, call, takeEvery } from 'redux-saga/effetcs';

// Create the set of async actions
const fetchTodosAsync = createAsyncAction(
  'FETCH_TODOS_REQUEST',
  'FETCH_TODOS_SUCCESS',
  'FETCH_TODOS_FAILURE'
)();

// Handle request saga
function* addTodoSaga(action: ReturnType): Generator {
  try {
    const response: Todo[] = yield call(todosApi.getAll, action.payload);

    yield put(fetchTodosAsync.success(response));
  } catch (err) {
    yield put(fetchTodosAsync.failure(err));
  }
}

// Main saga
function* mainSaga() {
    yield all([
        takeEvery(fetchTodosAsync.request, addTodoSaga),
    ]);
}

// Handle success reducer
export const todoReducer = createReducer({})
    .handleAction(fetchTodosAsync.success, (state, action) => ({ ...state, todos: action.payload }));

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---

API Docs v4 (v5 is WIP #189)

Action-Creators API

action

Simple action factory function to simplify creation of type-safe actions.

> WARNING:
> This approach will NOT WORK with action-helpers (such as getType and isActionOf) because it is creating action objects while all the other creator functions are returning enhanced action-creators.

action(type, payload?, meta?, error?)

Examples: > Advanced Usage Examples

const increment = () => action('INCREMENT');
// { type: 'INCREMENT'; }

const createUser = (id: number, name: string) =>
  action('CREATE_USER', { id, name });
// { type: 'CREATE_USER'; payload: { id: number; name: string }; }

const getUsers = (params?: string) =>
  action('GET_USERS', undefined, params);
// { type: 'GET_USERS'; meta: string | undefined; }

> TIP: Starting from TypeScript v3.4 you can achieve similar results using new as const operator.

const increment = () => ({ type: 'INCREMENT' } as const);

createAction

Create an enhanced action-creator with unlimited number of arguments.

• Resulting action-creator will preserve semantic names of their arguments (id, title, amount, etc...).
• Returned action object have predefined properties ({ type, payload, meta })

createAction(type)
createAction(type, actionCallback => {
  return (namedArg1, namedArg2, ...namedArgN) => actionCallback(payload?, meta?)
})

> TIP: Injected actionCallback argument is similar to action API but doesn't need the "type" parameter

Examples: > Advanced Usage Examples

import { createAction } from 'typesafe-actions';

// - with type only
const increment = createAction('INCREMENT');
dispatch(increment());
// { type: 'INCREMENT' };

// - with type and payload
const add = createAction('ADD', action => {
  return (amount: number) => action(amount);
});
dispatch(add(10));
// { type: 'ADD', payload: number }

// - with type and meta
const getTodos = createAction('GET_TODOS', action => {
  return (params: Params) => action(undefined, params);
});
dispatch(getTodos('some_meta'));
// { type: 'GET_TODOS', meta: Params }

// - and finally with type, payload and meta
const getTodo = createAction('GET_TODO', action => {
  return (id: string, meta: string) => action(id, meta);
});
dispatch(getTodo('some_id', 'some_meta'));
// { type: 'GET_TODO', payload: string, meta: string }

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createStandardAction

Create an enhanced action-creator compatible with Flux Standard Action to reduce boilerplate and enforce convention.

• Resulting action-creator have predefined arguments (payload, meta)
• Returned action object have predefined properties ({ type, payload, meta, error })
• But it also contains a .map() method that allow to map (payload, meta) arguments to a custom action object ({ customProp1, customProp2, ...customPropN })

createStandardAction(type)()
createStandardAction(type)()
createStandardAction(type).map((payload, meta) => ({ customProp1, customProp2, ...customPropN }))

> TIP: Using undefined as generic type parameter you can make the action-creator function require NO parameters.

Examples: > Advanced Usage Examples

import { createStandardAction } from 'typesafe-actions';

// Very concise with use of generic type arguments
// - with type only
const increment = createStandardAction('INCREMENT')();
const increment = createStandardAction('INCREMENT')();
increment(); // { type: 'INCREMENT' } (no parameters are required)


// - with type and payload
const add = createStandardAction('ADD')();
add(10); // { type: 'ADD', payload: number }

// - with type and meta
const getData = createStandardAction('GET_DATA')();
getData(undefined, 'meta'); // { type: 'GET_DATA', meta: string }

// - and finally with type, payload and meta
const getData = createStandardAction('GET_DATA')();
getData(1, 'meta'); // { type: 'GET_DATA', payload: number, meta: string }

// Can map payload and meta arguments to a custom action object
const notify = createStandardAction('NOTIFY').map(
  (payload: string, meta: Meta) => ({
    from: meta.username,
    message: `${username}: ${payload}`,
    messageType: meta.type,
    datetime: new Date(),
  })
);

dispatch(notify('Hello!', { username: 'Piotr', type: 'announcement' }));
// { type: 'NOTIFY', from: string, message: string, messageType: MessageType, datetime: Date }

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createCustomAction

Create an enhanced action-creator with unlimited number of arguments and custom properties on action object.

• Resulting action-creator will preserve semantic names of their arguments (id, title, amount, etc...).
• Returned action object have custom properties ({ type, customProp1, customProp2, ...customPropN })

createCustomAction(type, type => {
  return (namedArg1, namedArg2, ...namedArgN) => ({ type, customProp1, customProp2, ...customPropN })
})

Examples: > Advanced Usage Examples

import { createCustomAction } from 'typesafe-actions';

const add = createCustomAction('CUSTOM', type => {
  return (first: number, second: number) => ({ type, customProp1: first, customProp2: second });
});

dispatch(add(1));
// { type: "CUSTOM"; customProp1: number; customProp2: number; }

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createAsyncAction

Create an object containing three enhanced action-creators to simplify handling of async flows (e.g. network request - request/success/failure).

createAsyncAction(
  requestType, successType, failureType, cancelType?
)()

AsyncActionCreator

type AsyncActionCreator<
  [TRequestType, TRequestPayload],
  [TSuccessType, TSuccessPayload],
  [TFailureType, TFailurePayload],
  [TCancelType, TCancelPayload]?
> = {
  request: StandardActionCreator,
  success: StandardActionCreator,
  failure: StandardActionCreator,
  cancel?: StandardActionCreator,
}

> TIP: Using undefined as generic type parameter you can make the action-creator function require NO parameters.

Examples: > Advanced Usage Examples

import { createAsyncAction, AsyncActionCreator } from 'typesafe-actions';

const fetchUsersAsync = createAsyncAction(
  'FETCH_USERS_REQUEST',
  'FETCH_USERS_SUCCESS',
  'FETCH_USERS_FAILURE'
)();

dispatch(fetchUsersAsync.request(params));

dispatch(fetchUsersAsync.success(response));

dispatch(fetchUsersAsync.failure(err));

const fn = (
  a: AsyncActionCreator<
    ['FETCH_USERS_REQUEST', string],
    ['FETCH_USERS_SUCCESS', User[]],
    ['FETCH_USERS_FAILURE', Error]
  >
) => a;
fn(fetchUsersAsync);

// There is 4th optional argument to declare cancel action
const fetchUsersAsync = createAsyncAction(
  'FETCH_USERS_REQUEST',
  'FETCH_USERS_SUCCESS',
  'FETCH_USERS_FAILURE'
  'FETCH_USERS_CANCEL'
)();

dispatch(fetchUsersAsync.cancel('reason'));

const fn = (
  a: AsyncActionCreator<
    ['FETCH_USERS_REQUEST', string],
    ['FETCH_USERS_SUCCESS', User[]],
    ['FETCH_USERS_FAILURE', Error],
    ['FETCH_USERS_CANCEL', string]
  >
) => a;
fn(fetchUsersAsync);

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---

Reducer-Creators API

createReducer

Create a typesafe reducer

createReducer(initialState, handlersMap?)
// or
createReducer(initialState)
  .handleAction(actionCreator, reducer)
  .handleAction([actionCreator1, actionCreator2, ...actionCreatorN], reducer)
  .handleType(type, reducer)
  .handleType([type1, type2, ...typeN], reducer)

Examples: > Advanced Usage Examples

> TIP: You can use reducer API with a type-free syntax by Extending internal types, otherwise you'll have to pass generic type arguments like in below examples

// type-free syntax doesn't require generic type arguments
const counterReducer = createReducer(0, { 
  ADD: (state, action) => state + action.payload,
  [getType(increment)]: (state, _) => state + 1,
})

Object map style:

import { createReducer, getType } from 'typesafe-actions'

type State = number;
type Action = { type: 'ADD', payload: number } | { type: 'INCREMENT' };

const counterReducer = createReducer(0, { 
  ADD: (state, action) => state + action.payload,
  [getType(increment)]: (state, _) => state + 1,
})

Chain API style:

// using action-creators
const counterReducer = createReducer(0)
  .handleAction(add, (state, action) => state + action.payload)
  .handleAction(increment, (state, _) => state + 1)

  // handle multiple actions by using array
  .handleAction([add, increment], (state, action) =>
    state + (action.type === 'ADD' ? action.payload : 1)
  );

// all the same scenarios are working when using type-constants
const counterReducer = createReducer(0)
  .handleType('ADD', (state, action) => state + action.payload)
  .handleType('INCREMENT', (state, _) => state + 1);

Extend or compose reducers - every operation is completely typesafe:

const newCounterReducer = createReducer(0)
  .handleAction('SUBTRACT', (state, action) => state - action.payload)
  .handleAction('DECREMENT', (state, _) => state - 1);

const bigReducer = createReducer(0, {
  ...counterReducer.handlers, // typesafe
  ...newCounterReducer.handlers, // typesafe
  SUBTRACT: decrementReducer.handlers.DECREMENT, // <= error, wrong type
})

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---

Action-Helpers API

getType

Get the type property value (narrowed to literal type) of given enhanced action-creator.

getType(actionCreator)

> Advanced Usage Examples

Examples:

import { getType, createStandardAction } from 'typesafe-actions';

const add = createStandardAction('ADD')();

// In switch reducer
switch (action.type) {
  case getType(add):
    // action type is { type: "ADD"; payload: number; }
    return state + action.payload;

  default:
    return state;
}

// or with conditional statements
if (action.type === getType(add)) {
  // action type is { type: "ADD"; payload: number; }
}

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isActionOf

Check if action is an instance of given enhanced action-creator(s) (it will narrow action type to a type of given action-creator(s))

> WARNING: Regular action creators and action will not work with this helper

// can be used as a binary function
isActionOf(actionCreator, action)
// or as a curried function
isActionOf(actionCreator)(action)
// also accepts an array
isActionOf([actionCreator1, actionCreator2, ...actionCreatorN], action)
// with its curried equivalent
isActionOf([actionCreator1, actionCreator2, ...actionCreatorN])(action)

Examples: > Advanced Usage Examples

import { addTodo, removeTodo } from './todos-actions';

// Works with any filter type function (`Array.prototype.filter`, lodash, ramda, rxjs, etc.)
// - single action
[action1, action2, ...actionN]
  .filter(isActionOf(addTodo)) // only actions with type `ADD` will pass
  .map((action) => {
    // action type is { type: "todos/ADD"; payload: Todo; }
    ...
    
// - multiple actions
[action1, action2, ...actionN]
  .filter(isActionOf([addTodo, removeTodo])) // only actions with type `ADD` or 'REMOVE' will pass
  .do((action) => {
    // action type is { type: "todos/ADD"; payload: Todo; } | { type: "todos/REMOVE"; payload: Todo; }
    ...
      
// With conditional statements
// - single action
if(isActionOf(addTodo, action)) {
  return iAcceptOnlyTodoType(action.payload);
  // action type is { type: "todos/ADD"; payload: Todo; }
}
// - multiple actions
if(isActionOf([addTodo, removeTodo], action)) {
  return iAcceptOnlyTodoType(action.payload);
  // action type is { type: "todos/ADD"; payload: Todo; } | { type: "todos/REMOVE"; payload: Todo; }
}

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isOfType

Check if action type property is equal given type-constant(s) (it will narrow action type to a type of given action-creator(s))

// can be used as a binary function
isOfType(type, action)
// or as curried function
isOfType(type)(action)
// also accepts an array
isOfType([type1, type2, ...typeN], action)
// with its curried equivalent
isOfType([type1, type2, ...typeN])(action)

Examples: > Advanced Usage Examples

import { ADD, REMOVE } from './todos-types';

// Works with any filter type function (`Array.prototype.filter`, lodash, ramda, rxjs, etc.)
// - single action
[action1, action2, ...actionN]
  .filter(isOfType(ADD)) // only actions with type `ADD` will pass
  .map((action) => {
    // action type is { type: "todos/ADD"; payload: Todo; }
    ...
    
// - multiple actions
[action1, action2, ...actionN]
  .filter(isOfType([ADD, REMOVE])) // only actions with type `ADD` or 'REMOVE' will pass
  .do((action) => {
    // action type is { type: "todos/ADD"; payload: Todo; } | { type: "todos/REMOVE"; payload: Todo; }
    ...
      
// With conditional statements
// - single action
if(isOfType(ADD, action)) {
  return iAcceptOnlyTodoType(action.payload);
  // action type is { type: "todos/ADD"; payload: Todo; }
}
// - multiple actions
if(isOfType([ADD, REMOVE], action)) {
  return iAcceptOnlyTodoType(action.payload);
  // action type is { type: "todos/ADD"; payload: Todo; } | { type: "todos/REMOVE"; payload: Todo; }
}

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---

Type-Helpers API

Below helper functions are very flexible generalizations, works great with nested structures and will cover numerous different use-cases.

ActionType

Powerful type-helper that will infer union type from import * as ... or action-creator map object.

import { ActionType } from 'typesafe-actions';

// with "import * as ..."
import * as todos from './actions';
export type TodosAction = ActionType;
// TodosAction: { type: 'action1' } | { type: 'action2' } | { type: 'action3' }

// with nested action-creator map case
const actions = {
  action1: createAction('action1'),
  nested: {
    action2: createAction('action2'),
    moreNested: {
      action3: createAction('action3'),
    },
  },
};
export type RootAction = ActionType;
// RootAction: { type: 'action1' } | { type: 'action2' } | { type: 'action3' }

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StateType

Powerful type helper that will infer state object type from reducer function and nested/combined reducers.

> WARNING: working with redux@4+ types

import { combineReducers } from 'redux';
import { StateType } from 'typesafe-actions';

// with reducer function
const todosReducer = (state: Todo[] = [], action: TodosAction) => {
  switch (action.type) {
    case getType(todos.add):
      return [...state, action.payload];
    ...
export type TodosState = StateType;

// with nested/combined reducers
const rootReducer = combineReducers({
  router: routerReducer,
  counters: countersReducer,
});
export type RootState = StateType;

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---

Migration Guides

v4.x.x to v5.x.x

Breaking changes:

1. In v5 all the deprecated v4 creator functions are available under deprecated named import to help with incremental migration.

// before
import { createAction, createStandardAction, createCustomAction } from "typesafe-actions"

// after
import { deprecated } from "typesafe-actions"
const { createAction, createStandardAction, createCustomAction } = deprecated;

2. createStandardAction was renamed to createAction and .map method was removed in favor of simpler redux-actions style API.

// before
const withMappedPayloadAndMeta = createStandardAction(
  'CREATE_STANDARD_ACTION'
).map(({ username, message }: Notification) => ({
  payload: `${username}: ${message}`,
  meta: { username, message },
}));

// after
const withMappedPayloadAndMeta = createAction(
  'CREATE_STANDARD_ACTION',
  ({ username, message }: Notification) => `${username}: ${message}`, // payload creator
  ({ username, message }: Notification) => ({ username, message }) // meta creator
)();

3. v4 version of createAction was removed. I suggest to refactor to use a new createAction as in point 2, which was simplified and extended to support redux-actions style API.

// before
const withPayloadAndMeta = createAction('CREATE_ACTION', resolve => {
  return (id: number, token: string) => resolve(id, token);
});

// after
const withPayloadAndMeta = createAction(
  'CREATE_ACTION',
  (id: number, token: string) => id, // payload creator
  (id: number, token: string) => token // meta creator
})();

4. createCustomAction - API was greatly simplified, now it's used like this:

// before
const add = createCustomAction('CUSTOM', type => {
  return (first: number, second: number) => ({ type, customProp1: first, customProp2: second });
});

// after
const add = createCustomAction(
  'CUSTOM',
  (first: number, second: number) => ({ customProp1: first, customProp2: second })
);

5. AsyncActionCreator should be just renamed to AsyncActionCreatorBuilder.

// before
import { AsyncActionCreator } from "typesafe-actions"

//after
import { AsyncActionCreatorBuilder } from "typesafe-actions"

v3.x.x to v4.x.x

No breaking changes!

v2.x.x to v3.x.x

Minimal supported TypeScript v3.1+.

v1.x.x to v2.x.x

Breaking changes:

1. createAction

• In v2 we provide a createActionDeprecated function compatible with v1 createAction to help with incremental migration.

// in v1 we created action-creator like this:
const getTodo = createAction('GET_TODO',
  (id: string, meta: string) => ({
    type: 'GET_TODO',
    payload: id,
    meta: meta,
  })
);

getTodo('some_id', 'some_meta'); // { type: 'GET_TODO', payload: 'some_id', meta: 'some_meta' }

// in v2 we offer few different options - please choose your preference
const getTodoNoHelpers = (id: string, meta: string) => action('GET_TODO', id, meta);

const getTodoWithHelpers = createAction('GET_TODO', action => {
  return (id: string, meta: string) => action(id, meta);
});

const getTodoFSA = createStandardAction('GET_TODO')();

const getTodoCustom = createStandardAction('GET_TODO').map(
  ({ id, meta }: { id: string; meta: string; }) => ({
    payload: id,
    meta,
  })
);

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Migrating from redux-actions to typesafe-actions

• createAction(s)

createAction(type, payloadCreator, metaCreator) => createStandardAction(type)() || createStandardAction(type).map(payloadMetaCreator)

createActions() => // COMING SOON!

• handleAction(s)

handleAction(type, reducer, initialState) => createReducer(initialState).handleAction(type, reducer)

handleActions(reducerMap, initialState) => createReducer(initialState, reducerMap)

> TIP: If migrating from JS -> TS, you can swap out action-creators from redux-actions with action-creators from typesafe-actions in your handleActions handlers. This works because the action-creators from typesafe-actions provide the same toString method implementation used by redux-actions to match actions to the correct reducer.

• combineActions

Not needed because each function in the API accept single value or array of values for action types or action creators.

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---

Compatibility Notes

TypeScript support

• 5.X.X - TypeScript v3.2+
• 4.X.X - TypeScript v3.2+
• 3.X.X - TypeScript v3.2+
• 2.X.X - TypeScript v2.9+
• 1.X.X - TypeScript v2.7+

Browser support

It's compatible with all modern browsers.

For older browsers support (e.g. IE <= 11) and some mobile devices you need to provide the following polyfills:

• Object.assign
• Array.prototype.includes

Recommended polyfill for IE

To provide the best compatibility please include a popular polyfill package in your application, such as core-js or react-app-polyfill for create-react-app. Please check the React guidelines to learn how to do that: LINK A polyfill fo IE11 is included in our /codesandbox application.

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---

Recipes

Restrict Meta type in action creator

Using this recipe you can create an action creator with restricted Meta type with exact object shape.

export type MetaType = {
  analytics?: {
    eventName: string;
  };
};

export const actionWithRestrictedMeta = (
  type: T,
  payload: P,
  meta: MetaType
) => action(type, payload, meta);

export const validAction = (payload: string) =>
  actionWithRestrictedMeta('type', payload, { analytics: { eventName: 'success' } }); // OK!

export const invalidAction = (payload: string) =>
  actionWithRestrictedMeta('type', payload, { analytics: { excessProp: 'no way!' } }); // Error
// Object literal may only specify known properties, and 'excessProp' does not exist in type '{ eventName: string; }

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---

Compare to others

Here you can find out a detailed comparison of typesafe-actions to other solutions.

redux-actions

Lets compare the 3 most common variants of action-creators (with type only, with payload and with payload + meta)

Note: tested with "@types/redux-actions": "2.2.3"

- with type only (no payload)

redux-actions

const notify1 = createAction('NOTIFY');
// resulting type:
// () => {
//   type: string;
//   payload: void | undefined;
//   error: boolean | undefined;
// }

> with redux-actions you can notice the redundant nullable payload property and literal type of type property is lost (discrimination of union type would not be possible)

typesafe-actions

const notify1 = () => action('NOTIFY');
// resulting type:
// () => {
//   type: "NOTIFY";
// }

> with typesafe-actions there is no excess nullable types and no excess properties and the action "type" property is containing a literal type

- with payload

redux-actions

const notify2 = createAction('NOTIFY',
  (username: string, message?: string) => ({
    message: `${username}: ${message || 'Empty!'}`,
  })
);
// resulting type:
// (t1: string) => {
//   type: string;
//   payload: { message: string; } | undefined;
//   error: boolean | undefined;
// }

> first the optional message parameter is lost, username semantic argument name is changed to some generic t1, type property is widened once again and payload is nullable because of broken inference

typesafe-actions

const notify2 = (username: string, message?: string) => action(
  'NOTIFY',
  { message: `${username}: ${message || 'Empty!'}` },
);
// resulting type:
// (username: string, message?: string | undefined) => {
//   type: "NOTIFY";
//   payload: { message: string; };
// }

> typesafe-actions infer very precise resulting type, notice working optional parameters and semantic argument names are preserved which is really important for great intellisense experience

- with payload and meta

redux-actions

const notify3 = createAction('NOTIFY',
  (username: string, message?: string) => (
    { message: `${username}: ${message || 'Empty!'}` }
  ),
  (username: string, message?: string) => (
    { username, message }
  )
);
// resulting type:
// (...args: any[]) => {
//   type: string;
//   payload: { message: string; } | undefined;
//   meta: { username: string; message: string | undefined; };
//   error: boolean | undefined;
// }

> this time we got a completely broken arguments arity with no type-safety because of any type with all the earlier issues

typesafe-actions

/**
 * typesafe-actions
 */
const notify3 = (username: string, message?: string) => action(
  'NOTIFY',
  { message: `${username}: ${message || 'Empty!'}` },
  { username, message },
);
// resulting type:
// (username: string, message?: string | undefined) => {
//   type: "NOTIFY";
//   payload: { message: string; };
//   meta: { username: string; message: string | undefined; };
// }

> typesafe-actions never fail to any type, even with this advanced scenario all types are correct and provide complete type-safety and excellent developer experience

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---

Motivation

When I started to combine Redux with TypeScript, I was trying to use redux-actions to reduce the maintainability cost and boilerplate of action-creators. Unfortunately, the results were intimidating: incorrect type signatures and broken type-inference cascading throughout the entire code-base (click here for a detailed comparison).

Existing solutions in the wild have been either too verbose because of redundant type annotations (hard to maintain) or used classes (hinders readability and requires using the new keyword 😱)

So I created typesafe-actions to address all of the above pain points.

The core idea was to design an API that would mostly use the power of TypeScript type-inference 💪 to lift the "maintainability burden" of type annotations. In addition, I wanted to make it "look and feel" as close as possible to the idiomatic JavaScript ❤️ , so we don't have to write the redundant type annotations that which will create additional noise in your code.

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---

Contributing

You can help make this project better by contributing. If you're planning to contribute please make sure to check our contributing guide: CONTRIBUTING.md

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---

Funding Issues

You can also help by funding issues. Issues like bug fixes or feature requests can be very quickly resolved when funded through the IssueHunt platform.

I highly recommend to add a bounty to the issue that you're waiting for to increase priority and attract contributors willing to work on it.

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---

License

MIT License

Copyright (c) 2017 Piotr Witek (https://piotrwitek.github.io)