mindfront-redux-utils

Making Redux scalable

If you use combineReducers to create your top-level reducer, it will call every one of your subreducers for every action you dispatch. This is easy to debug, and it ensures your state will update correctly, but it's easy to imagine how it will create performance problems.

Imagine you're combining 100 subreducers, and you're dispatching actions from a mousemove listener at 60 Hz. That's 6000 subreducer calls per second, and it only increases as you add more slices to your state and corresponding subreducers to your app.

This package and mindfront-redux-utils-immutable help you create and combine reducers and middleware in such a way that only the relevant subreducer(s) and middleware for a given action are called, so you don't have to worry that performance will decrease with every subreducer or sub-subreducer (etc) you add.

There is a downside to this approach: debugging is more difficult, because it's harder to trace where a subreducer is getting called from (or why it's not getting called). This package tries to mitigate that problem as much as it can by saving stack traces of where reducers were created and combined.

Legacy build note

If you are building for legacy browsers with webpack or similar bundlers, make sure to add a rule to transpile this package with babel.

createReducer([initialState: any,] actionHandlers: {[actionType: string]: Reducer}): Reducer

import { createReducer } from 'mindfront-redux-utils'

Creates a reducer that delegates to actionHandlers[action.type], if it exists, and otherwise, returns state. If initialState is provided, it will be used as the initial state if the reducer is called with undefined initial state.

The returned reducer will also have initialState and actionHandlers as own properties (primarily so that composeReducers can efficiently compose action map reducers).

composeReducers(...reducers: Reducer[]): Reducer

import { composeReducers } from 'mindfront-redux-utils'

Creates a reducer that applies all the provided reducers.

If any consecutive reducers have an actionHandlers property that is an object (for instance reducers made with createReducer), composeReducers will compose them efficiently: it will group the action handlers by type, compose the handlers for each type separately, and then use createReducer on the composed action handlers, and initial state from the first reducer for which initialState is defined.

createMiddleware(actionHandlers: {[actionType: string]: Middleware}): Middleware

import { createMiddleware } from 'mindfront-redux-utils'

Creates middleware that delegates to actionHandlers[action.type], if it exists, and otherwise, returns next(action).

The returned middleware will also have actionHandlers as an own property.

composeMiddleware(...middlewares: Middleware[]): Middleware

import { composeMiddleware } from 'mindfront-redux-utils'

Composes the given middlewares to be called one after another, just like Redux' applyMiddleware, but with one optimization: sequences of consecutive middleware that have actionHandlers will be recombined into a single middleware that calls any actionHandlers for a given action directly.

applyMiddleware(...middlewares: Middleware[]): createStore => createStore'

Requires redux as an optional dependency.

import applyMiddleware from 'mindfront-redux-utils/lib/applyMiddleware'

Just like applyMiddleware from redux, but applies the same optimization as composeMiddleware: sequences of consecutive middleware that have actionHandlers will be recombined into a single middleware that calls any actionHandlers for a given action directly.

combineMiddlewareWithActionHandlers(...middlewares: Middleware[]): Middleware[]

import { combineMiddlewareWithActionHandlers } from 'mindfront-redux-utils'

Replaces any sequences of consecutive middleware that have actionHandlers in the arguments with a single middleware that calls the actionHandlers for a given action directly. (This is used by composeMiddleware under the hood).

createPluggableMiddleware(initialMiddleware: Middleware): Middleware

import { createPluggableMiddleware } from 'mindfront-redux-utils'

Creates a middleware that delegates to a hot-swappable middleware. The returned middleware will have a replaceMiddleware(nextMiddleware: Middleware) function. This way you can use Webpack hot reloading on your custom middleware.

prefixReducer(prefix: string): (reducer: Reducer) => Reducer

import { prefixReducer } from 'mindfront-redux-utils'

A reducer decorator that strips prefix from each action.type before passing it to the decorated reducer. If the action.type doesn't start with prefix, it will just return the state instead of calling reducer.

If the decorated reducer has actionHandlers (from createReducer), then the returned reducer will have actionHandlers with the prefixed action type keys.

Example

import { combineReducers } from 'redux'
import { createReducer, prefixReducer } from 'mindfront-redux-utils'

const counterReducer = createReducer(0, {
  DECREMENT: (state) => state - 1,
  INCREMENT: (state) => state + 1,
})

const reducer = combineReducers({
  counter1: prefixReducer('COUNTER_1.')(counterReducer),
  counter2: prefixReducer('COUNTER_2.')(counterReducer),
})

reducer({}, { type: 'COUNTER_1.INCREMENT' }) // {counter1: 1}
reducer({ counter1: 3, counter2: 3 }, { type: 'COUNTER_1.DECREMENT' }) // {counter1: 2, counter2: 3}
reducer({ counter1: 3, counter2: 3 }, { type: 'COUNTER_2.INCREMENT' }) // {counter1: 3, counter2: 4}

prefixActionCreator(prefix: string): (actionCreator: ActionCreator) => ActionCreator

import { prefixActionCreator } from 'mindfront-redux-utils'

An action creator decorator that prepends prefix to the type of the created actions.

Example

import { prefixActionCreator } from 'mindfront-redux-utils'

function setEntry(key, value) {
  return {
    type: 'SET_ENTRY',
    payload: value,
    meta: { key },
  }
}

const setConfigEntry = prefixActionCreator('CONFIG.')(setEntry)

setConfigEntry('hello', 'world').type // CONFIG.SET_ENTRY

addMeta(meta: Object): (actionCreator: ActionCreator) => ActionCreator

import { addMeta } from 'mindfront-redux-utils'

An action or action creator decorator that assigns additional properties to actions' meta.

Example

import { addMeta } from 'mindfront-redux-utils'

function setEntry(key, value) {
  return {
    type: 'SET_ENTRY',
    payload: value,
    meta: { key },
  }
}

const forConfigDomain = addMeta({ domain: 'config' })

const setConfigEntry = forConfigDomain(setEntry)

setConfigEntry('hello', 'world').meta // {key: 'hello', domain: 'config'}

forConfigDomain(setEntry('hello', 'world')).meta // {key: 'hello', domain: 'config'}

fullStack(error: Error, wrapped?: (error: Error) => string): string

Errors thrown from the sub-reducers you pass to createReducer, composeReducers, 'prefixReducer', or sub-middleware you pass to createMiddleware or composeMiddleware normally don't include any information about where the associated call to createReducer etc. occurred, making debugging difficult. However, in dev mode, mindfront-redux-utils adds this info to the resulting reducers and middleware, and you can get it by calling fullStack, like so:

import { createReducer, fullStack } from './src'

function hello() {
  throw new Error('TEST')
}
const r = createReducer({ hello })

try {
  r({}, { type: 'hello' })
} catch (e) {
  console.error(fullStack(e))
}

Output:

Error: TEST
    at hello (/Users/andy/redux-utils/temp.js:4:9)
    at result (/Users/andy/redux-utils/src/createReducer.js:19:24)
    at withCause (/Users/andy/redux-utils/src/addCreationStack.js:5:14)
    at Object.<anonymous> (/Users/andy/redux-utils/temp.js:9:3)
    at Module._compile (module.js:556:32)
    at loader (/Users/andy/redux-utils/node_modules/babel-register/lib/node.js:144:5)
    at Object.require.extensions.(anonymous function) [as .js] (/Users/andy/redux-utils/node_modules/babel-register/lib/node.js:154:7)
    at Module.load (module.js:473:32)
    at tryModuleLoad (module.js:432:12)
    at Function.Module._load (module.js:424:3)
Caused by reducer created at:
    at addCreationStack (/Users/andy/redux-utils/src/addCreationStack.js:2:21)
    at createReducer (/Users/andy/redux-utils/src/createReducer.js:25:55)
    at Object.<anonymous> (/Users/andy/redux-utils/temp.js:6:11)
    at Module._compile (module.js:556:32)
    at loader (/Users/andy/redux-utils/node_modules/babel-register/lib/node.js:144:5)
    at Object.require.extensions.(anonymous function) [as .js] (/Users/andy/redux-utils/node_modules/babel-register/lib/node.js:154:7)
    at Module.load (module.js:473:32)
    at tryModuleLoad (module.js:432:12)
    at Function.Module._load (module.js:424:3)
    at Function.Module.runMain (module.js:590:10)

If you are using VError, you may pass VError's fullStack function as the second argument to also include the cause chain from VError.