immutable-reducers

Create reducers for immutable data structures. Useful for redux.

Table of contents

• Install
• Use
• createReducer
• combineReducers
• Use
• Contributing
• Thanks
• License

Install

npm install --save immutable-reducers

Use

import { fromJS } from 'immutable';
import { combineReducers, createReducer } from 'immutable-reducers';
 
// Setup some state (probably your app state)
 
const initialState = fromJS({
    artist: {
        name: {
            first: 'Sean',
            last: 'Combs'
        },
        fans: 0
    }
});
 
// Create some reducers
 
const artistNameReducer = createReducer(['artist', 'name'], (state, action) => {
    switch (action.type) {
        case 'RENAME':
            return fromJS(action.value);
    }
    return state;
});
 
// You can scope them by combining with an object
 
const artistFansReducer = createReducer(['artis', 'fans'], (state, action) => {
    switch (action.type) {
        case 'NEW_FAN':
            return state + action.count;
    }
    return state;
});
 
// Combine 'em up
 
const reducer = combineReducers(artistNameReducer, artistFansReducer);
 
// Step the state
 
reducer(initialState, { type: 'NEW_FAN', count: 1 });
 

createReducer

createReducer helps you make a reducer that operates on a small area of an immutable data structure.

createReducer(
    keyPath: Array<any>,
    updater: (targetState: any, action: Object) => any,
    state: any
): any

For example, given some initial state:

const initialState = fromJS({
    user: {
        favorites: Immutable.OrderedSet()
    }
});

We can create a reducer that looks out for favorite actions and remembers the id:

const favoriteReducer = createReducer(['user', 'favorites'], (favorites, action) => {
    switch (action.type) {
        case 'FAVORITE':
            return favorites.add(action.id);
    }
    return favorites;
});

createReducer handles reaching into the data structure and updating the value.

Good to know:

• If the updater function returns the same value it was called with, then no change will occur.
• If the keyPath you specify does not exist, an Immutable Map will be created at each intermediary key.
• The keys can be immutable data structures too #winning
• The third argument to the reducer is the whole state object, allowing you consult other areas of state when handling an action

combineReducers

combineReducers is a less opinionated version of redux's default combineReducers utility.

type Reducer = (state: any, action: Object) => any;
type ReducerObject = Object<string, Reducer>;
 
combineReducers(...Reducer|ReducerObject): Reducer

It has two useful forms: applied to a list of reducers or to an object. When applied to the list, it acts like redux's combineReducers.

When applied to an object, it's slightly different. immutable-reducers will use the key of the object to 'scope' the reducer further.

For example, in the following example: You could scope it to the user key of your (immutable) state using combineReducers:

const combineReducer = combineReducers({
    user: createReducer(['favorites'], (favorites, action) => {
        switch (action.type) {
            case 'FAVORITE':
                return favorites.add(action.id);
        }
        return favorites;
    });
});

The end result is the same as the createReducers example, where the favoritesReducer will actually operate on the ['user', 'favorites'] key path.

Contributing

Please read the contribution guidelines. Contributions are welcome!

Thanks

Thanks to rackt for redux and all those who work on immutable.

License

Copyright (c) 2015 Tom Ashworth. Released under the MIT license.