feature-state is a straightforward, typesafe, and feature-based state management library for ReactJs.

• Lightweight & Tree Shakable: Function-based and modular design (< 1KB minified)
• Fast: Minimal code ensures high performance, and state changes can be deferred in "the bucket"
• Modular & Extendable: Easily extendable with features like withStorage(), withUndo(), ..
• Typesafe: Build with TypeScript for strong type safety
• Standalone: Zero dependencies, ensuring ease of use in various environments

📚 Examples

• ReactJs Counter (Code Sandbox)

🌟 Motivation

Create a typesafe, straightforward, and lightweight state management library designed to be modular and extendable with features like withStorage(), withUndo(), .. Having previously built AgileTs, I realized the importance of simplicity and modularity. AgileTs, while powerful, became bloated and complex. Learning from that experience, I followed the KISS (Keep It Simple, Stupid) principle for feature-state, aiming to provide a more streamlined and efficient solution. Because no code is the best code.

⚖️ Alternatives

• nanostores
• jotai
• AgileTs

📖 Usage

store/tasks.ts

import { createState } from 'feature-state';

export const $tasks = createState<Task[]>([]);

export function addTask(task: Task) {
	$tasks.set([...$tasks.get(), task]);
}

components/Tasks.tsx

import { useGlobalState } from 'feature-state-react';

import { $tasks } from '../store/tasks';

export const Tasks = () => {
	const tasks = useGlobalState($tasks);

	return (
		<ul>
			{tasks.map((task) => (
				<li>{task.title}</li>
			))}
		</ul>
	);
};

Atom-based

States in feature-state are atom-based, meaning each state should only represent a single piece of data. They can store various types of data such as strings, numbers, arrays, or even objects.

To create an state, use createState(initialValue) and pass the initial value as the first argument.

import { createState } from 'feature-state';

export const $temperature = createState(20); // °C

In TypeScript, you can optionally specify the value type using a type parameter.

export type TWeatherCondition = 'sunny' | 'cloudy' | 'rainy';

export const $weatherCondition = createState<TWeatherCondition>('sunny');

To get the current value of the state, use $state.get(). To change the value, use $state.set(nextValue).

$temperature.set($temperature.get() + 5);

Subscribing to State Changes

You can subscribe to state changes using $state.subscribe(callback), which works in vanilla JS. For React, special hooks like useGlobalState($state) are available to re-render components on state changes.

Listener callbacks will receive the new value as the first argument.

const unsubscribe = $temperature.subscribe((newValue) => {
	console.log(`Temperature changed to ${newValue}°C`);
});

Unlike $state.listen(callback), $state.subscribe(callback) immediately invokes the listener during the subscription.

📙 Features

withStorage()

Adds persistence functionality to the state, allowing the state to be saved to and loaded from a storage medium.

import { createState, withStorage } from 'feature-state';

const storage = {
	async save(key, value) {
		localStorage.setItem(key, JSON.stringify(value));
		return true;
	},
	async load(key) {
		const value = localStorage.getItem(key);
		return value ? JSON.parse(value) : undefined;
	},
	async delete(key) {
		localStorage.removeItem(key);
		return true;
	}
};

const state = withStorage(createState([]), storage, 'tasks');

await state.persist();

state.addTask({ id: 1, title: 'Task 1' });

• storage: An object implementing the StorageInterface with methods save, load, and delete for handling the persistence
• key: The key used to identify the state in the storage medium

withUndo()

Adds undo functionality to the state, allowing the state to revert to previous values.

import { createState, withUndo } from 'feature-state';

const state = withUndo(createState([]), 50);

state.addTask({ id: 1, title: 'Task 1' });
state.undo();

• historyLimit: The maximum number of states to keep in history for undo functionality. The default is 50

withMultiUndo()

Adds multi-undo functionality to the state, allowing the state to revert to multiple previous values at once.

import { createState, withMultiUndo, withUndo } from 'feature-state';

const state = withMultiUndo(withUndo(createState([]), 50));

state.addTask({ id: 1, title: 'Task 1' });
state.addTask({ id: 2, title: 'Task 2' });
state.multiUndo(2);

• count: The number of undo steps to perform, reverting the state back by the specified number of changes