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React useSharedState (Jotai inspired)
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| // like useState but shared by several compoments | |
| // inspired by Jotai, | |
| function createUseSharedState(value) { | |
| let _value = value; | |
| const _subs = new Map() | |
| function useSharedState() { | |
| const self = React.useRef({}); | |
| const selfForceUpdate = React.useReducer(x=>!x, false)[1] | |
| React.useEffect(()=>{ | |
| console.log('sub') | |
| _subs.set(self.current, selfForceUpdate) | |
| return ()=>{ | |
| console.log('unsub') | |
| _subs.delete(self.current); | |
| } | |
| },[]) | |
| return [ | |
| _value, | |
| (fnNewValue)=>{ | |
| _value = fnNewValue(_value); | |
| _subs.forEach((v,k)=>{ | |
| console.log('sub exec'); | |
| v() // forceupdates | |
| }); | |
| } | |
| ] | |
| } | |
| return useSharedState; | |
| } | |
| // -- EXAMPLE: Initialize, outside a React comonot | |
| const useCounter = createUseSharedState(3); | |
| // -- and use it in a component like useState | |
| const Comp1 = ()=>{ | |
| const [count, setCount] = useCounter(); | |
| return <button onClick={()=>setCount(s=>s+1)}>{count}</button> | |
| } | |
| // See live example: https://codepen.io/drodsou/pen/dyJvaNq | |
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| // Online example: https://codepen.io/drodsou/pen/dyJvaNq | |
| // Local example: | |
| // npm create vite@latest example1 -- --template react && cd example1 && npm install | |
| // paste this in src/App.jsx | |
| import React from 'react'; | |
| // -- lib | |
| function createUseSharedState(value) { | |
| let _value = value; | |
| const _subs = new Map() | |
| function useSharedState() { | |
| const self = React.useRef({}); | |
| const selfForceUpdate = React.useReducer(x=>!x, false)[1] | |
| React.useEffect(()=>{ | |
| console.log('sub') | |
| _subs.set(self.current, selfForceUpdate) | |
| return ()=>{ | |
| console.log('unsub') | |
| _subs.delete(self.current); | |
| } | |
| },[]) | |
| return [ | |
| _value, | |
| (fnNewValue)=>{ | |
| _value = fnNewValue(_value); | |
| _subs.forEach((v,k)=>{ | |
| console.log('sub exec'); | |
| v() // forceupdates | |
| }); | |
| } | |
| ] | |
| } | |
| return useSharedState; | |
| } | |
| // -- Example | |
| const useCounter = createUseSharedState(3); | |
| // window.useCounter = useCounter; | |
| function App () { | |
| const [appState, setAppState] = React.useState(true) | |
| const Comp1 = ()=>{ | |
| // const [count, setCount] = React.useState(0); | |
| const [count, setCount] = useCounter(); | |
| return <button onClick={()=>setCount(s=>s+1)}>{count}</button> | |
| } | |
| const Comp2 = ()=>{ | |
| // const [count, setCount] = React.useState(0); | |
| const [count, setCount] = useCounter(); | |
| return <button onClick={()=>setCount(s=>s+1)}>{count}</button> | |
| } | |
| return ( | |
| <> | |
| <h1>useSharedState</h1> | |
| <p>Open console to see traces</p> | |
| <button onClick={()=>setAppState(s=>!s)}> toggle counters</button> | |
| {appState && <div> | |
| <Comp1/> | |
| <Comp2/> | |
| </div>} | |
| <style dangerouslySetInnerHTML={{__html: ` | |
| body { background-color: black; color: white; font-family: sans-serif;} | |
| button {font-size:20px; margin: 10px; padding: 5px 20px; cursor: pointer;} | |
| `}}/> | |
| </> | |
| ) | |
| } | |
| export default App; |
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