Imm

Write better reducers!

Imm is a set of tools to help you simplify your reducers. It works with all flux-style architectures, including Redux, Recompose's withReducer and React's useReducer hook.

Installation

Just add @mariosant/imm to your package.json.

$ npm install @mariosant/imm

# or
$ yarn add @mariosant/imm

You can now import the module and use it like

import { createReducer, when } from '@mariosant/imm';

// or if you are on node or browserify
const { createReducer, when } = require('@mariosant/imm');

Usage

Using imm is pretty straightforward and simple. All it requires, is to dispatch actions that comply with the Flux Standard Action.

import { createReducer, when } from '@mariosant/imm';

const initialState = {};

const reducer = createReducer([
	when('SET_NAME', (state, { payload }) => ({ ...state, name: payload })),
	when('SET_EMAIL', (state, { payload }) => ({ ...state, email: payload })),
], initialState);

or even better:

import { createAction, createReducer, when, select } from '@mariosant/imm';
const SET_NAME = 'SET_NAME';
const SET_EMAIL = 'SET_EMAIL';

const initialState = {};

const setUserNameAction = createAction(SET_NAME);
const setUserName = (state, { payload }) =>
	select(['user', 'name'], _name => payload, state);

// dot notation for paths work as well
const setUserEmailAction = createAction(SET_EMAIL);
const setUserEmail = (state, { payload }) =>
	select('user.email', _email => payload, state);

const reducer = createReducer([
	when(SET_NAME, setUserName),
	when(SET_EMAIL, setUserEmail),
], initialState);

The first argument passed to when, can be a String or a Function. If it is a String, it compares it with the type of your dispatched action. If it is an actionCreator, it uses it to get its type and executes the associated transfomer.

Here is an example.

import { createReducer, when, createAction } from '@mariosant/imm';
import { propEq } from 'ramda';

const email = createAction('SET_EMAIL');

const setName = (state, { payload }) => ({ ...state, name: payload });
const setEmail = (state, { payload }) => ({ ...state, email: payload });
const setAge = (state, { payload }) => ({ ...state, age: payload });

const reducer = createReducer(when('SET_NAME', setName), when(email, setEmail));

By using this paradigm, you have less things to worry about. You don't have to care about multiple return statements and you only have to test your transformers and if you use the feature, your predicates,

Development

Easy enough!

$ yarn install  # to install dependencies
$ yarn test     # to run the test suite

Meta

Marios Antonoudiou – @marios_ant – mariosant@sent.com

Distributed under the MIT license.

https://github.com/mariosant/imm

Contributing

1. Fork it (https://github.com/mariosant/imm/fork)
2. Create your feature branch (git checkout -b feature/fooBar)
3. Commit your changes using a semantic commit message.
4. Push to the branch (git push origin feature/fooBar)
5. Create a new Pull Request