• [Javascript] Simplify Creating Immutable Data Trees With Immer


    Immer is a tiny library that makes it possible to work with immutable data in JavaScript in a much more straight-forward way by operating on a temporarily draft state and using all the normal JavaScript API's and data structures. The first part of the lesson explains how to use Immer, and the second part of the lesson shows you how it can be used to simplify, for example, Redux reducers.

    Immer has a few unique features:

    • Supports arbitrary, deep modifications in immutable data trees
    • Strongly typed
    • Uses JavaScript native data structures, no new API to learn
    • Automatically freezes any data that is produced

    The whole point of Immer is that you can wrap you reducer function with the function immer provide, let's call 'produce'.  When you call it, if you don't do anything, it just return your previous state, if you do any partial mutation, if will keep original object untouched, instead creating immutable version return to you. therefore make code much simpler.

    // Before
    
    const byId = (state, action) => {
      switch (action.type) {
        case RECEIVE_PRODUCTS:
          return {
            ...state,
            ...action.products.reduce((obj, product) => {
              obj[product.id] = product
              return obj
            }, {})
          }
        default:
          return state
      }
    }
    // After
    
    import produce from 'immer'
    
    const byId = (state, action) =>
      produce(state, draft => {
        switch (action.type) {
          case RECEIVE_PRODUCTS:
            action.products.forEach(product => {
              draft[product.id] = product
            })
        }
      })

    Or an improved version:

    import produce from 'immer'
    
    const byId = produce((draft, action) => {
      switch (action.type) {
        case RECEIVE_PRODUCTS:
        action.products.forEach(product => {
            draft[product.id] = product
        })
      }
    })
  • 相关阅读:
    第八章:模型视图
    第二章:初识Qt
    第三章:正式开始
    第七章:QtQuick控件
    第十章:形状
    第六章:Fluid元素
    第一章:前言
    第九章:画布
    weblogic基于https访问其他servers时无法访问
    ssh远程连接网络构建 wang
  • 原文地址:https://www.cnblogs.com/Answer1215/p/8285359.html
Copyright © 2020-2023  润新知