Reducer Builder

This package provides an efficient way to make complex reducers by combining a hierarchy of reducers. Using map of action types to small reducers that actually handle the give types, reducer-recipe produces more CPU-efficient (not benchmarked) reducers than the ones created by combileReducers(). On every action, combineReducers() calls all the small reducers, each with some switch-case structure without considering the fact that most of the small reducers actually doesn't handle the given action type. Moreover, this package let you make reducers in a different code-style if you like to avoid large switch-case/if-else statements.

Recipes

A recipe is a function that takes a builder (r) as argument and gives r instructions on how it should generate the desired reducer. To do so, recipe should call:

1. r.default(state): with the default value for state.
2. r.on(actionType, reducer(state, action)): to tell the builder how the final reducer should handle an action of given type.

import builder from 'reducer-recipe';

const Artist = (r) => {
    r.default({ name: 'Unknown', followers: 0, albums: [] })
        .on('set-artist-name', (state, action) => {
            return { ...state, name: action.name };
        })
        .on('set-artist-followers', (state, action) => {
            return { ...state, followers: action.followers };
        })
        .on('publish-new-album', (state, action) => {
            return { ...state, albums: [...state.albums, action.album] };
        });
};

const artistReducer = builder.build(Artist);

The code above generates the following reducer:

const artistReducer = (state = { name: 'Unknown', followers: 0, albums: [] }, action) => {
    switch (action.type) {
      case 'set-artist-name':
        return { ...state, name: action.name };
      case 'set-artist-followers':
        return { ...state, followers: action.followers };
      case 'publish-new-album':
        return { ...state, albums: [...state.albums, action.album] };
      default:
        return state;
    }
}

Combine recipes and reducers

To make a bigger recipe from smaller recipes you can use builder.combine() function:

const combinedRecipe = builder.combine({ Album, Artist});
const combinedReducer = builder.build(combinedRecipe);

Alternatively, you can call builder.buildCombined() to combine rececipes and build the reducer at once:

const combinedReducer = builder.buildCombined({ Album, Artist});

If for some reason, you need pure reducers that cannot be built from recipes, and you want to mix them with recipes, you can pass them as second argument to builder.combine() or builder.buildCombined():

const News = (state = [], action) => {
    switch (action.type) {
        case 'add-news':
            return [action.news, ...state];
        case 'pop-news':
            let newState = [...state];
            newState.pop();
            return newState;
        default:
            return state;
    }
};

const reducer = builder.buildCombined({ Album, Artist }, { News });

See the tests file to see a complete example.