proxy-reducer

Using Proxy API to auto construct new State for Redux Reducer

Inspired by Immer by smaller in bundle size; Powered by use-state-proxy

Installation

## using npm
npm install proxy-reducer

## or using yarn
yarn add proxy-reducer

## or using pnpm
pnpm install proxy-reducer

Typescript Signature

// auto construct new state when updater carry out in-place update
export function proxyReducer<T extends object>(
  state: T,
  updater: (state: T) => void,
): T

Features

• [x] Support Reducer of Redux
• [x] Auto construct new state when invoking mutating methods on state fields
  • [x] Array
  • [x] Map
  • [x] Set
  • [x] Date
  • [x] Object
  • [X] Custom Classes
• [x] Tested with @testing-library/jest-dom

Comparison

With proxy-reducer

In the reducer, you can call proxyReducer() with the state and a updater() function. In the updater(), you can get/set the values, and call mutating methods (e.g. array.push()) directly.

proxyReducer() will auto construct a new state (on-demand) and return as reducer result.

Usage Example:

import { proxyReducer } from 'proxy-reducer'

export const reducer = (state, action) => {
  return proxyReducer(state, state => {
    switch (action.type) {
      case 'set':
        state.text = action.text
        return
      case 'push':
        state.list.push(state.text)
        state.text = ''
        return
      case 'del':
        state.list.slice(action.i, 1)
        return
      default:
        return
    }
  })
}

Using proxyReducer(), the array can be updated with state.list.push(action.text) and state.list.slice(action.i, 1) directly. This invokes proxied methods, and it will auto construct new state.

Without proxy-reducer

You need to construct new states by explicitly copying the old fields and setting new values.

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

export const reducer = (state, action) => {
  switch (action.type) {
    case 'set':
      return {
        ...state,
        text: action.text,
      }
    case 'push':
      return {
        ...state,
        text: '',
        list: [...state.list, state.text],
      }
    case 'del': {
      return {
        ...state,
        list: state.list.filter((_, j) => action.i !== j)
      }
    }
    default:
      return state
  }
}

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

Details refers to demo-custom-mutable-class.ts in use-state-proxy

License

BSD-2-Clause (Free Open Source Software)