Xoid

xoid is a framework-agnostic state management library. X 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

or

yarn add xoid

Examples

• Counter

• Todos (Basic)

• Todos (Filtered)

• Celcius-Fahrenheit conversion

• Finite state stopwatch

• Dots and arrows

• Transient update resize observer

• xoid vs useReducer vs useMethods

Quick Tutorial

xoid has only one export: create. Create is also exported as the default export.

import { create } from 'xoid' import create from 'xoid'

Atom

Atoms are holders of state.

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 if the second argument is used.

import { create } from 'xoid'

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

numberAtom.actions.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 alphaAtom = atom.focus(s => s.deeply.nested.alpha)
alphaAtom.set(6)

// 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) }
)

// later
unsub()

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's similar to React.useMemo with empty dependencies array. It'll run its callback only once.

import { useSetup } from '@xoid/react'

const App = () => {
  const $counter = useSetup(() => create(5))

  ...
}

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

An outer value can be supplied as the second argument. It'll turn into a reactive atom.

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)
  }, props)

  ...
}

If you've read until here, you have 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 } = atom.actions // 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
• @xoid/feature - A typesafe plugin system oriented in ES6 classes

Thanks

Following awesome projects inspired xoid a lot.

• Recoil
• zustand
• mobx-state-tree

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