jotai-molecules has been renamed to bunshi.

All new users of this module should use bunshi instead. Bunshi adds support for vue, react and vanilla javascript. Development and features additions will continue under the bunshi package.

Molecules in jotai-molecules version 1.2.0 are compatible with molecules from bunshi, and they can interoperated and depend on each others. Version 1.2.0 of jotai-molecules is just a wrapper for bunshi.

Documentation: bunshi.org

A tiny, fast, dependency-free 1.18kb library for creating jotai atoms in a way that lets you lift state up, or push state down. See Motivation for more details on why we created this library.

Installation

This module is published on NPM as jotai-molecules

npm i jotai-molecules

Note: Prefer bunshi to jotai-molecules

Usage

Molecules are a set of atoms that can be easily scoped globally or per context.

import React from "react";
import { atom, useAtom } from "jotai";
import {
  molecule,
  useMolecule,
  createScope,
  ScopeProvider,
} from "jotai-molecules";

const CompanyScope = createScope<string>("example.com");

const CompanyMolecule = molecule((_, getScope) => {
  const company = getScope(CompanyScope);
  const companyNameAtom = atom(company.toUpperCase());
  return {
    company,
    companyNameAtom,
  };
});

const UserScope = createScope<string>("[email protected]");

const UserMolecule = molecule((getMol, getScope) => {
  const userId = getScope(UserScope);
  const companyAtoms = getMol(CompanyMolecule);
  const userNameAtom = atom(userId + " name");
  const userCountryAtom = atom(userId + " country");
  const groupAtom = atom((get) => {
    return userId + " in " + get(companyAtoms.companyNameAtom);
  });
  return {
    userId,
    userCountryAtom,
    userNameAtom,
    groupAtom,
    company: companyAtoms.company,
  };
});

const App = () => (
  <ScopeProvider scope={UserScope} value={"[email protected]"}>
    <UserComponent />
  </ScopeProvider>
);

const UserComponent = () => {
  const userAtoms = useMolecule(UserMolecule);
  const [userName, setUserName] = useAtom(userAtoms.userNameAtom);

  return (
    <div>
      Hi, my name is {userName} <br />
      <input
        type="text"
        value={userName}
        onInput={(e) => setUserName((e.target as HTMLInputElement).value)}
      />
    </div>
  );
};

API

molecule

Create a molecule that can be dependent on other molecules, or dependent on scope.

import { molecule } from "jotai-molecules";

export const PageMolecule = molecule(() => {
  return {
    currentPage: atom("/"),
    currentParams: atom({}),
  };
});

• Requires a getter function
  • getMol - depend on the value of another molecule
  • getScope - depend on the value of a scope

useMolecule

Use a molecule for the current scope. Will produce a different value depending on the React context it is run in.

import { useMolecule } from "jotai-molecules";
import { useSetAtom, useAtomValue } from "jotai";

export const PageComponent = () => {
  const pageAtoms = useMolecule(PageMolecule);

  const setParams = useSetAtom(pageAtoms.currentPage);
  const page = useAtomValue(pageAtoms.currentPage);

  return (
    <div>
      Page: {page}
      <br />
      <button onClick={() => setParams({ date: Date.now() })}>
        Set current time
      </button>
    </div>
  );
};

By default useMolecule will provide a molecule based off the implicit scope from context. You can override this behaviour by passing options to useMolecule.

• withScope - will overide a scope value (ScopeTuple<unknown>)
• withUniqueScope - will override a scope value with a new unique value (MoleculeScope<unknown>)
• exclusiveScope - will override ALL scopes (ScopeTuple<unknown>)

Instead of a scope provider, you can use an explicit scope when using a molecule. This can simplify integrating jotai with other hooks-based libraries.

Before:

const App = () => (
  <ScopeProvider scope={UserScope} value={"[email protected]"}>
    <UserComponent />
  </ScopeProvider>
);

After:

useMolecule(UserMolecule, { withScope: [UserScope, "[email protected]"] });

createScope

Creates a reference for scopes, similar to React Context

import { createScope } from "jotai-molecules";

/**
 *  Scope for a user id
 */
export const UserScope = createScope<string>("[email protected]");

• initialValue the default value for molecules that depend on this scope

ScopeProvider

Provides a new value for Scope, similar to React Context. This will create new molecules in the react tree that depend on it.

const App = () => (
  <ScopeProvider scope={UserScope} value={"[email protected]"}>
    <UserComponent />
  </ScopeProvider>
);

• scope the MoleculeScope reference to provide
• value a new value for that scope