Morphium

Morphium is a framework-agnostic, type-safe, and mutable state management library. It aims to simplify the state mutations compared to the existing immutable state management libraries like Redux & Zustand.

It is very similar to the existing Valtio library, it uses Proxy under the hood to track the state changes and notify the subscribers, and it was basically created for learning purposes.

Usage

In order to create a mutable state object, use the morph function:

import { morph } from 'morphium';

const state = morph({
  firstName: 'John',
  lastName: 'Doe',
  age: 42,
  address: {
    city: 'New York',
    country: 'USA',
  },
});

Then, you can listen to state changes using the subscribe function. It accepts the mutable state instance, and a subscriber function that will be called whenever the state changes. The subscriber function will receive an array of paths that represent the properties that have changed:

import { subscribe } from 'morphium';

const unsubscribe = subscribe(state, (paths) => {
  paths.forEach((path) => {
    console.log('state.' + path.join('.') + ' has changed');
  });
});

state.address.city = 'Los Angeles';
state.age++;

// Logs:
// 'state.address.city has changed'
// 'state.age has changed'

unsubscribe();

Subscriptions are batched by default, which is why you get an array of paths rather than a single one. If you want to get notified for each individual path, you can pass false as the third argument to the subscribe function:

import { subscribe } from 'morphium';

subscribe(
  state,
  (path) => {
    console.log('state.' + path.join('.') + ' has changed');
  },
  false,
);

state.address.city = 'Los Angeles'; // Logs: 'state.address.city has changed'
state.age++; // Logs: 'state.age has changed'

For convenience, there is also a type-safe get function that lets you read from the morphed object based on the path you get in the subscriber function:

import { subscribe, get } from 'morphium';

subscribe(state, (paths) => {
  paths.forEach((path) => {
    const pathAsString = path.join('.');
    const value = get(state, path);

    console.log(`state.${pathAsString} has changed to ${value}`);
  });
});

Usage with React

In order to use Morphium with React, use the useSnapshot hook. This hook will subscribe only to the properties that are accessed in the component, and it will re-render the component whenever those properties change:

import { morph } from 'morphium';
import { useSnapshot } from 'morphium/react';

const state = morph({
  name: 'counter',
  count: 0,
});

function Counter() {
  const snapshot = useSnapshot(state);

  // Will re-render the `Counter` component.
  return <button onClick={() => state.count++}>{snapshot.count}</button>;
}

function OtherComponent() {
  // Will NOT re-render the `Counter` component.
  return (
    <button onClick={() => (state.name = 'new-counter')}>Change name</button>
  );
}

Note that the useSnapshot hook is also batched, so your component will only re-render once even if multiple properties have changed.