【整理と共有】人気のReact状態管理ツール7選

import React from "react"
import ReactDOM from "react-dom"
import { makeAutoObservable } from "mobx"
import { observer } from "mobx-react-lite"

class Timer {
    secondsPassed = 0

    constructor() {
        makeAutoObservable(this)
    }

    increaseTimer() {
        this.secondsPassed += 1
    }
}

const myTimer = new Timer()

//被`observer`包裹的函数式组件会被监听在它每一次调用前发生的任何变化
const TimerView = observer(({ timer }) => 
           <span>Seconds passed: {timer.secondsPassed}
</span>)

ReactDOM.render(<TimerView timer={myTimer} />, document.body)

import { createStore } from 'redux'

/**
 * This is a reducer - a function that takes a current state value and an
 * action object describing "what happened", and returns a new state value.
 * A reducer's function signature is: (state, action) => newState
 *
 * The Redux state should contain only plain JS objects, arrays, and primitives.
 * The root state value is usually an object. It's important that you should
 * not mutate the state object, but return a new object if the state changes.
 *
 * You can use any conditional logic you want in a reducer. In this example,
 * we use a switch statement, but it's not required.
 */
function counterReducer(state = { value: 0 }, action) {
  switch (action.type) {
    case 'counter/incremented':
      return { value: state.value + 1 }
    case 'counter/decremented':
      return { value: state.value - 1 }
    default:
      return state
  }
}

// Create a Redux store holding the state of your app.
// Its API is { subscribe, dispatch, getState }.
let store = createStore(counterReducer)

// You can use subscribe() to update the UI in response to state changes.
// Normally you'd use a view binding library (e.g. React Redux) rather than subscribe() directly.
// There may be additional use cases where it's helpful to subscribe as well.

store.subscribe(() => console.log(store.getState()))

// The only way to mutate the internal state is to dispatch an action.
// The actions can be serialized, logged or stored and later replayed.
store.dispatch({ type: 'counter/incremented' })
// {value: 1}
store.dispatch({ type: 'counter/incremented' })
// {value: 2}
store.dispatch({ type: 'counter/decremented' })
// {value: 1}

import { createModel } from "@rematch/core";
import { RootModel } from ".";

export const count = createModel<RootModel>()({
  state: 0, // initial state
  reducers: {
    // handle state changes with pure functions
    increment(state, payload: number) {
      return state + payload;
    },
  },
  effects: (dispatch) => ({
    // handle state changes with impure functions.
    // use async/await for async actions
    async incrementAsync(payload: number, state) {
      console.log("This is current root state", state);
      await new Promise((resolve) => setTimeout(resolve, 1000));
      dispatch.count.increment(payload);
    },
  }),
});

import React from 'react';
import {
  RecoilRoot,
  atom,
  selector,
  useRecoilState,
  useRecoilValue,
} from 'recoil';

function App() {
  return (
    <RecoilRoot>
      <CharacterCounter />
    </RecoilRoot>
  );
}

const textState = atom({
  key: 'textState', // unique ID (with respect to other atoms/selectors)
  default: '', // default value (aka initial value)
});

function CharacterCounter() {
  return (
    <div>
      <TextInput />
      <CharacterCount />
    </div>
  );
}

function TextInput() {
  const [text, setText] = useRecoilState(textState);

  const onChange = (event) => {
    setText(event.target.value);
  };

  return (
    <div>
      <input type="text" value={text} onChange={onChange} />
      <br />
      Echo: {text}
    </div>
  );
}

import { atom, useAtom } from 'jotai';

const countAtom = atom(0);

function Counter() {
  const [count, setCount] = useAtom(countAtom);

  return (
    <div>
      <h1>Count: {count}</h1>

      <button onClick={() => setCount(count + 1)}>Increment</button>

      <button onClick={() => setCount(count - 1)}>Decrement</button>
    </div>
  );
}

import create from 'zustand'

const useStore = create((set) => ({
  count: 0,
  increment: () => set((state) => ({ count: state.count + 1 })),
  decrement: () => set((state) => ({ count: state.count - 1 })),
}))

function Counter() {
  const { count, increment, decrement } = useStore()

  return (
    <div>
      <h1>Count: {count}</h1>
      <button onClick={increment}>Increment</button>
      <button onClick={decrement}>Decrement</button>
    </div>
  )
}