redux-promised-thunk

Thunk middleware which is support functions and Promises for Redux. Originally based on [redux-thunk](middleware.

npm install --save redux-promised-thunk

What's a thunk?!

A thunk is a function that wraps an expression to delay its evaluation.

// calculation of 1 + 2 is immediate
// x === 3
let x = 1 + 2;

// calculation of 1 + 2 is delayed
// foo can be called later to perform the calculation
// foo is a thunk!
let foo = () => 1 + 2;

Usage

redux-promised-thunk middleware allows you to write action creators that return a thunk instead of an action. The thunk can be used to delay the dispatch of an action, or to dispatch only if a certain condition is met. The thunk receives the store methods dispatch and getState() as parameters.

An action creator that returns a thunk to perform asynchronous dispatch:

const INCREMENT_COUNTER = 'INCREMENT_COUNTER';

function increment() {
  return {
    type: INCREMENT_COUNTER
  };
}

function incrementAsync() {
  return dispatch => {
    setTimeout(() => {
      // Yay! Can invoke sync or async actions with `dispatch`
      dispatch(increment());
    }, 1000);
  };
}

An action creator that returns a thunk to perform conditional dispatch:

function incrementIfOdd() {
  return (dispatch, getState) => {
    const { counter } = getState();

    if (counter % 2 === 0) {
      return;
    }

    dispatch(increment());
  };
}

But you can also return async functions:

function incrementIfOdd() {
  return async (dispatch, getState) => {
    const { counter } = getState();

    const result = await shouldIncrement(counter);
    if (!result)
      return;
    }

    dispatch(increment());
  };
}

To enable redux-promised-thunk use applyMiddleware():

import { createStore, applyMiddleware, combineReducers } from 'redux';
import PromisedThunk from 'redux-promised-thunk';
import * as reducers from './reducers/index';

const reducer = combineReducers(reducers);

// create a store that has redux-thunk middleware enabled
const actionPromises = [];
const createStoreWithMiddleware = applyMiddleware(
  PromisedThunk((promisedAction, action, store) => {
    actionPromises.push(promisedAction);
  }
)(createStore);

const store = createStoreWithMiddleware(reducer);

License

MIT