react-palm

A cohesive strategy for managing state, handling side effects, and testing React Apps.

⚠️ This is work in progress, please don't bother me about it, thanks. ⚠️

yarn add react-palm

Setup

Add the taskMiddleware to your store, or the tasks handlers won't get called.

import { createStore, applyMiddleware, compose } from 'redux'
import { taskMiddleware } from 'react-palm'

import reducer from './reducer'

// using createStore
const store = createStore(reducer, applyMiddleWare(taskMiddleware))

// using enhancers
const initialState = {}
const middlewares = [taskMiddleware]
const enhancers = [
  applyMiddleware(...middlewares)
]

const store = createStore(reducer, initialState, compose(...enhancers))

Usage

Here is a sample of what a delay task which triggers an action after a specified amount of time would look like.

import { taskCreator } from 'react-palm'

export const DELAY = taskCreator((time, success) =>
  new Promise(resolve => setTimeout(resolve, time))
    .then(() => success()), 'DELAY');

You can use the task in your reducer like this:

import { withTask } from 'react-palm'
import { handleActions, createAction } from 'react-palm/actions'

import {DELAY} from './tasks/delay'

export const incrementWithDelay = createAction('DELAY_INCREMENT')
const increment = createAction('INCREMENT')

handleActions({
  DELAY_INCREMENT: state =>
    withTask(state, DELAY(1000).map(increment)),

  INCREMENT: state => state + 1
}, 0)

Dispatching incrementWithDelay will wait one second, then increment our counter state.

The call to .map tells us to wrap the result of the task in an INCREMENT action.

In the above example, we directly pass state as the first argument to withTask. Whatever you pass as the first argument will become the updated state, so you can update your state before the task is executed if you want. This might be useful to update a loading spinner, for instance.

Testing

We designed react-palm with testing in mind. Since you probably don't want to create API calls in a testing environment, we provide a drainTasksForTesting utility that will remove all the tasks from the queue and return them.

You can now assert that they have the expected type and payload.

import { drainTasksForTesting } from 'react-palm'

import reducer, { incrementWithDelay } from './reducer'
import DELAY from './tasks/delay'

test('The delay task should be valid', t => {
  const state = reducer(42, incrementWithDelay())
  const tasks = drainTasksForTesting()

  t.is(state, 42)
  t.is(tasks.length, 1)
  t.is(tasks[0].type, DELAY)
  t.is(tasks[0].action.type, 'INCREMENT')

  const newState = reducer(state, task.action)
  t.is(newState, 43)
})

You can also have a look to the example directory for a complete use-case.

FAQ

Strategy? Framework? Library?

It's unlikely that you'll create a cohesive architecture if you piecemeal add requirements to an existing design.

react-palm takes a "subtractive" approach; we start with a full set of concerns and make sure that they work well together before breaking them up. This means that as your app grows, you won't have to rethink everything.

Should I use this?

Ideally, you should use Elm or PureScript. This architecture is the closest thing to Elm I've managed to make within the constraints of JavaScript, React, and Redux. I created it as a stop-gap for specific applications that I work on. It contains trade-offs that may not be generally useful.

• Elm, a friendly, functional, compile-to-JS language.
  • The Elm Architecture (TEA)
• PureScript, a feature-rich, functional compile-to-JS language.
• Choo, a small, Elm-like framework for JavaScript.
• redux-loop a library that provides a very literal translation of commands and tasks from Elm to Redux.