xoid: A TypeScript repository from utkusahinformsort

xoid is a framework-agnostic state management library. X (though it's read as Z) in its name signifies the inspiration it draws from great projects such as ReduX, MobX and Xstate. It was designed to be simple and scalable. It has extensive Typescript support.

xoid is lightweight (~1kB gzipped), but quite powerful. It's composed of building blocks for advanced state management patterns. One of the biggest aims of xoid is to unify global state, local component state, and finite state machines in a single API. While doing all these, it also aims to keep itself approachable for newcomers. More features are explained below, and the documentation website.

To install, run the following command:

npm install xoid

yarn add xoid

Examples

Quick Tutorial

xoid has only 2 exports: create and use. This section will cover them, and the @xoid/react.

Atom

Atoms are holders of state. create function is used to create them.

import { create } from 'xoid'

const atom = create(3)
console.log(atom.value) // 3
atom.set(5)
atom.update(state => state + 1)
console.log(atom.value) // 6

Atoms can have actions, and with .use method they can be used.

import { create, use } from 'xoid'

const numberAtom = create(5, (atom) => ({
  increment: () => atom.update(s => s + 1),
  decrement: () => atom.update(s => s - 1)
}))

use(numberAtom).increment()

There's the .focus method, which can be used as a selector/lens. xoid is based on immutable updates, so if you "surgically" set state of a focused branch, changes will propagate to the root.

import { create } from 'xoid'

const atom = create({ deeply: { nested: { alpha: 5 } } })
const previousValue = atom.value

// select `.deeply.nested.alpha`
const alpha = atom.focus(s => s.deeply.nested.alpha)
alpha.set(s => s + 1)

// root state is replaced with new immutable state
assert(atom.value !== previousValue) // ✅
assert(atom.value.deeply.nested.alpha === 6) // ✅

Derived state

Atoms can be derived from other atoms. This API was heavily inspired by Recoil.

const alpha = create(3)
const beta = create(5)
// derived atom
const sum = create((get) => get(alpha) + get(beta))

Alternatively, .map method can be used to quickly derive the state from a single atom.

const alpha = create(3)
// derived atom
const doubleAlpha = alpha.map((s) => s * 2)

Subscriptions

For subscriptions, subscribe and watch are used. They are the same, except watch runs the callback immediately, while subscribe waits for the first update after subscription.

const unsub = atom.subscribe(
  (state, previousState) => { console.log(state, previousState) }
)

To cleanup side-effects, a function can be returned in the subscriber function. (Just like React.useEffect)

React integration

@xoid/react is based on two hooks. useAtom subscribes the component to an atom. If a second argument is supplied, it'll be used as a selector function.

import { useAtom } from '@xoid/react'

// in a React component
const state = useAtom(atom)

The other hook is useSetup. It can be used for creating local component state. It'll run its callback only once. If a second argument is supplied, it'll be used for communication between the closure (useSetup scope) and outside (React component scope).

import { useSetup } from '@xoid/react'

const App = (props: Props) => {
  const setup = useSetup(($props) => {
    // `$props` has the type: Atom<Props>
    // this way, we can react to `props.something` as it changes
    $props.focus(s => s.something).subscribe(console.log)

    const alpha = create(5)
    return { alpha }
  }, props)

  ...
}

useSetup is guaranteed to be non-render-causing. Atoms returned by that should be explicitly subscribed via useAtom hook.

Here, this is enough knowledge to start using xoid! You can refer to the documentation website for more.

More features

Pattern: Finite state machines

No additional syntax is required for state machines. Just use the good old create function.

import { create } from 'xoid'
import { useAtom } from '@xoid/react'

const createMachine = () => {
  const red = { color: '#f00', onClick: () => atom.set(green) }
  const green = { color: '#0f0', onClick: () => atom.set(red) }
  const atom = create(red)
  return atom
}

// in a React component
const { color, onClick } = useAtom(createMachine)
return <div style={{ color }} onClick={onClick} />

Redux Devtools integration

Import @xoid/devtools and set a debugValue to your atom. It will send values to the Redux Devtools Extension.

import { devtools } from '@xoid/devtools'
import { create, use } from 'xoid'
devtools() // run once

const atom = create(
  { alpha: 5 }, 
  (atom) => {
    const $alpha = atom.focus(s => s.alpha)
    return {
      inc: () => $alpha.update(s => s + 1),
      resetState: () => atom.set({ alpha: 5 })
      deeply: {
        nested: {
          action: () => $alpha.set(5)
        }
      } 
    }
  }
)

atom.debugValue = 'myAtom' // enable watching it by the devtools

const { deeply, incrementAlpha } = use(atom) // destructuring is no problem
incrementAlpha() // logs "(myAtom).incrementAlpha"
deeply.nested.action() // logs "(myAtom).deeply.nested.action"
atom.focus(s => s.alpha).set(25)  // logs "(myAtom) Update ([timestamp])

Why xoid?

Easy to learn
Small bundle size
Framework-agnostic
Extensive Typescript support
Easy to work with nested states
Computed values, transient updates
Can be used to express finite state machines
No middleware is required for async/generator stuff
Global state and local component state in the same API

Other packages

@xoid/react - React integration
@xoid/devtools - Redux Devtools integration
@xoid/lite - Lighter version with less features intended for library authors
@xoid/feature - A typesafe plugin system oriented in ES6 classes

Thanks

Following awesome projects inspired xoid a lot.

Thanks to Anatoly for the pencil&ruler icon #24975.

utkusahinformsort/xoid