@godsboss/redux-reducer-map v0.0.3

About

Build a reducer out of a map of reducer functions.

Installation

npm install --save @godsboss/redux-reducer-map

Usage

Initial state

When creating the reducer, you have to give it an initial state which is returned when the combined reducer is called with an undefined state:

import createMapReducer from '@godsboss/redux-reducer-map'
import { createStore } from 'redux'

const reducerMap = {}
const initialState = { value: 123 }
const store = createStore(createMapReducer(reducerMap, initialState))

let value = store.getState().value // 123

Combining reducers

Given some actions and reducers:

// Action types
const INC = "INC"
const DEC = "DEC"

// Action creators
const createInc = (value) => ({ type: INC, value })
const createDec = (value) => ({ type: DEC, value })

// Reducing functions
const inc = (state, action) => ({ value: state.value + action.value })
const dec = (state, action) => ({ value: state.value - action.value })

Create a map of your reducing functions, action types are property names:

let reducerMap = {}
reducerMap[INC] = inc
reducerMap[DEC] = dec

Then create the reducer, the store, and use it:

import createMapReducer from '@godsboss/redux-reducer-map'
import { createStore } from 'redux'

const initialState = { value: 0 }
const store = createStore(createMapReducer(reducerMap, initialState))

store.dispatch(createInc(200))
store.getState().value // 200

store.dispatch(createDec(150))
store.getState().value // 50

Unknown action types

By default, calling the reducer with an unknown action type (i.e. not found in the map) throws an error:

import createMapReducer from '@godsboss/redux-reducer-map'
import { createStore } from 'redux'

const reducerMap = {}
const initialState = {}
const store = createStore(createMapReducer(reducerMap, initialState))

const action = { type: "NOT_FOUND" }
try {
  store.dispatch(action)
} catch (error) {
  console.log(error.state)
  console.log(error.action)
}

This is by design. Unknown action types very likely point to a design and/or programming error, like a misspelling (you do use action creators, right?) or a forgotten action still dispatched somewhere.

But this is configurable, there is an optional third parameter which is a reducer-like callback:

const onUnknownAction = (state, action) => {
  console.log('Unknown action!', state, action)
  return state
}
const store = createStore(createMapReducer(reducerMap, initialState, onUnknownAction))

There is a convenience function which just returns the state:

const store = createStore(createMapReducer(reducerMap, initialState, createMapReducer.justReturnState))

Running the tests

npm install
npm test

Development

Tests can be found in test. Pull requests without accompanying tests will be rejected.

The library source code is inside the src directory. It is then compiled via npm run-script build (npm install beforehand is needed) into the dist folder.