use-state-proxy

Using Proxy API to auto dispatch React.useState(). Inspired from @State() in @stencil/core.

Installation

## using npm
npm install use-state-proxy

## or using yarn
yarn add use-state-proxy

## or using pnpm
pnpm install use-state-proxy

Typescript Signature

type StateProxy<T extends object> = T

// auto trigger re-render when in-place update occurs
export function useStateProxy<T extends object>(initialValue: T): StateProxy<T>

// return the object reference to the initialValue
export function unProxy<T extends object>(proxy: StateProxy<T>): T

Features

• Auto trigger re-render when invoking mutating methods on state fields
  • Array
  • Map
  • Set
  • Date
  • Object
  • Custom Classes
• Create a variant for shared state, as simpler alternative to redux store (using redux or context)
• Tested with @testing-library/jest-dom

Comparison

With use-state-proxy

You can get/set the values, and call mutating methods (e.g. array.push()) directly.

The 'setState' action is auto dispatched when the value is changed, which auto trigger re-rendering.

Usage Example:

import React from 'react'
import { useStateProxy } from 'use-state-proxy'

function DemoUseStateProxy() {
  const state = useStateProxy({
    text: '',
    list: ['init']
  })
  const { list } = state
  return <>
    <input
      value={state.text}
      onChange={e => state.text = e.target.value}
    />
    <button onClick={() => [list.push(state.text), state.text = '']}>
      Save
    </button>
    <ul>
      {list.map((item, i) => <li key={i}>
        <button onClick={() => list.splice(i, 1)}>Delete</button>
        <span>{item}</span>
        <input
          value={item}
          onChange={(e) => [
            (state.list[i] = e.target.value),
            (state.list = state.list),
          ]}
        />
      </li>)}
    </ul>
  </>
}

export default DemoUseStateProxy

Using useStateProxy(), the array can be updated with state.list.push(state.text) and state.list.splice(i, 1) directly. This invokes proxied methods, and it will auto trigger re-rendering.

Without use-state-proxy

You need to set up the states one-by-one, and explicitly call the setHooks to trigger re-rendering.

Moreover, there is syntax noise when updating complex data type, e.g. Array, Map, Set, and Object.

import React, { useState } from 'react'

function DemoUseState() {
  const [text, setText] = useState('')
  const [list, setList] = useState(['init'])
  return <>
    <input value={text} onChange={e => setText(e.target.value)} />
    <button onClick={() => [setList([...list, text]), setText('')]}>
      Save
    </button>
    <ul>
      {list.map((item, i) => <li key={i}>
        <button onClick={() => setList(list.filter((_, j) => i !== j))}>
          Delete
        </button>
        <span>{item}</span>
        <input
          value={item}
          onChange={(e) => {
            const newList = [...list];
            newList[i] = e.target.value;
            setList(newList);
          }}
        />
      </li>)}
    </ul>
  </>
}

export default DemoUseState

In this example, in order to 'push' an item to the list, it manually destructs the original array with spread syntax ... then append the new item at the end.

Also, to remove an item from the list, it constructs a new array with list.filter(), involving multiple levels of array indices, which is error-prone.

The same hurdles applies to object as well, and it gets even worse when it comes to Set* and Map**.

*: To update a Set, we can run setList(new Set([...list, item])) or setList(new Set([...list].filter(x => x !== target)))

**: To update a Map, we can run setList(new Map([...list, [key, value]])) or setList(new Map([...list].filter(([key]) => key !== target)))

Register Mutating Methods on Custom Classes

The mutating methods of custom classes can be registered. This mechanism allows use-state-proxy to auto trigger re-rendering even when the state consists of non-json values. (Array, Map, Set and Date are supported by default.)

Below demo how to register mutating methods on WeakSet with registerMutableMethodsByClassConstructor() and registerMutableMethodsByClassName():

import {
  registerMutableMethodsByClassConstructor,
  registerMutableMethodsByClassName
} from 'use-state-proxy'

let mutableWeakSetMethods: Array<keyof typeof WeakSet.prototype> = [
  'add',
  'delete',
]
registerMutableMethodsByClassConstructor(WeakSet, methods)
registerMutableMethodsByClassName('[object WeakSet]', methods) // to support cross-frame objects

You can also use helper functions getClassName() and registerPrimitiveMutableClass() to avoid typo mistakes.

import { getClassName, registerPrimitiveMutableClass } from 'use-state-proxy'

registerPrimitiveMutableClass(WeakSet, getClassName(new WeakSet()), ['add', 'delete'])

Details see demo-custom-mutable-class.ts

Todo

• Refactor into typical react-library structure https://medium.com/better-programming/build-your-very-own-react-component-library-and-publish-it-to-github-package-registry-192a688a51fd

License

BSD-2-Clause (Free Open Source Software)