模拟购物车

功能点

显示购物列表
加入购物车
从购物车删除

设计模式

工厂模式
单例模式
装饰器模式
观察者模式
状态模式
模板方法模式
代理模式

UML类图

classDiagram

Demo --> App
App <-- List
App <-- ShoppingCart
Item <-- List
Cart <-- Item
ShoppingCart --> Cart

class Demo {
  + app: App
  +main () void
}

class App {
  +init() void
  -initShoppingCart() void
  -initList() void
}

class List {
  - app: App
  +init() void
  -loadData() Promise
  -initItemList(data) void
  -render() void
}

class Item {
  - list: List
  - data: Object
  - cart: Cart
  +init() void
  -initShoppingCart() void
  -initList() void
  -addToCartHandler() void
  -deleteFromCartHandler() void
  -render() void
}

class Cart {
  - list: Array
  + add(data) void
  + del(id) void
  + getList(): String
}

class ShoppingCart {
  - app: App
  - cart: Cart
  +init() void
  -initBtn() void
  -showCart() void
  -render() void
}

实践

目录结构

index.js
index.html
- Demo
  - List
    - CreateItem.js
    - Item.js
    - List.js
  - ShoppingCart
    - GetCart.js
    - ShoppingCart.js
  - util
    - log.js
  - App.js
  - data.json

代码

index.html 入口模板

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>模拟购物车</title>
</head>
<body>
  <div id="app"></div>
</body>
<script src="./index.js"></script>
</html>

index.js 入口文件

import App from './demo/App.js'

const app = new App('app')
app.init('app')

商品处理 demo/List/CreateItem.js

import Item from './Item.js'

// 工厂函数 - 工厂模式
export default function (list, itemData) {
  if (itemData.discount) {
    itemData = createDiscount(itemData)
  }
  return new Item(list, itemData)
}

// 代理模式, 感觉这里用有些生硬
const createDiscount = itemData => {
  return new Proxy(itemData, {
    get: (target, key) => {
      if (key === 'name') {
        return `${target[key]}【折扣💰】`
      }
      if (key === 'price') {
        return target[key] * 0.8
      }
      return target[key]
    }
  })
}

商品列表项类 demo/List/Item.js

import getCart from '../ShoppingCart/GetCart.js'
import StateMachine from 'javascript-state-machine'
import { log } from './../util/log.js'
export default class Item {
  constructor(list, data) {
    this.list = list
    this.data = data
    this.$el = document.createElement("DIV")
    this.cart = getCart && getCart()
  }

  initContent() {
    const $el = this.$el
    const data = this.data
    const nameDom = document.createElement("P")
    nameDom.innerHTML = `名称：${data.name}`
    const priceDom = document.createElement("P")
    priceDom.innerHTML = `价格：${data.price}`
    $el.append(nameDom)
    $el.append(priceDom)
  }

  initBtn() {
    const $el = this.$el
    const btn = document.createElement("BUTTON")

    // 状态模式
    const fsm = new StateMachine({
      init: '加入购物车',
      transitions: [
        {
          name: 'addToCart',
          from: '加入购物车',
          to: '从购物车删除'
        },
        {
          name: 'deleteFromCart',
          from: '从购物车删除',
          to: '加入购物车'
        }
      ],
      methods: {
        // 加入购物车
        onAddToCart: () => {
          this.addToCartHandler()
          updateText()
        },
        // 从购物车删除
        onDeleteFromCart: () => {
          this.deleteFromCartHandler()
          updateText()
        }
      }
    })

    const updateText = () => {
      btn.innerHTML = fsm.state
    }
    btn.onclick = () => {
      // 添加到购物车
      if (fsm.is('加入购物车')) {
        fsm.addToCart()
      // 从购物车移除
      } else if (fsm.is('从购物车删除')) {
        fsm.deleteFromCart()
      }
    }
    updateText()
    $el.append(btn)
  }

  @log('add')
  addToCartHandler() {
    this.cart.add(this.data)
  }

  @log('del')
  deleteFromCartHandler() {
    this.cart.del(this.data.id)
  }

  render() {
    this.list.$el.append(this.$el)
  }

  init() {
    this.initContent()
    this.initBtn()
    this.render()
  }
}

商品列表类 demo/List/List.js

import goodsData from './../data.json'
import createItem from './CreateItem.js'

export default class List {
  constructor(app) {
    this.app = app
    this.$el = document.createElement("DIV")
  }

  // 获取数据
  loadData() {
    return new Promise(resolve => {
      resolve(goodsData)
    })
  }

  // 生成列表
  initItemList(data) {
    data.forEach(itemData => {
      const item = createItem(this, itemData)
      item.init()
    })
  }

  // 渲染
  render() {
    this.app.$el.append(this.$el)
  }

  async init() {
    const data = await this.loadData()
    this.initItemList(data)
    this.render()
  }
}

购物车类（内存逻辑） demo/ShoppingCart/GetCart.js

// 购物车内存
class Cart {
  constructor() {
    this.list = [];
  }

  add(data) {
    this.list.push(data)
  }

  del(id) {
    const delIndex = this.list.findIndex(x => x.id === id)
    this.list.splice(delIndex, 1)
  }

  getList() {
    return this.list.map(x => x.name)
  }

  getCart() {
    return cartInstance
  }
}

let cartInstance = null

// 返回单例 - 单例模式
const getCart = (() => () => {
  if (!cartInstance) {
    cartInstance = new Cart()
  }
  return cartInstance
})()

export default getCart

购物车容器类 demo/ShoppingCart/shoppingCart.js

import getCart from '../ShoppingCart/GetCart.js'

export default class ShoppingCart {
  constructor(app) {
    this.app = app
    this.$el = document.createElement('div')
    this.cart = getCart && getCart()
  }

  initBtn() {
    const btnDom = document.createElement('button')
    btnDom.innerHTML = '购物车'
    btnDom.onclick = () => {
      this.showCart()
    }
    this.$el.append(btnDom)
  }

  showCart() {
    console.log(this.cart.getList())
  }

  render() {
    this.app.$el.append(this.$el)
  }

  init() {
    this.initBtn()
    this.render()
  }
}

日志上报处理 demo/util/log.js

// 装饰器模式
const log = type => (target, name, descriptor) => {
  const oldValue = descriptor.value
  descriptor.value = function() {
    console.log(`日志上报 ${type}`)
    return oldValue.apply(this, arguments)
  }
  return descriptor
}

export { log }

App 类 demo/App.js

import ShoppingCart from './ShoppingCart/ShoppingCart'
import List from './List/List'

export default class App {
  constructor(id) {
    this.$el = document.getElementById(`${id}`);
  }

  // 初始化购物车
  initShoppingCart() {
    const shoppingCart = new ShoppingCart(this)
    shoppingCart.init()
  }

  // 初始化列表
  initList() {
    const list = new List(this)
    list.init()
  }

  init() {
    this.initShoppingCart()
    this.initList()
  }
}

mock 数据 demo/data.json

[
  {
    "id": 1,
    "name": "aaa",
    "price": 111,
    "discount": 1
  },
  {
    "id": 2,
    "name": "bbb",
    "price": 222,
    "discount": 1
  },
  {
    "id": 3,
    "name": "ccc",
    "price": 333,
    "discount": 0
  },
  {
    "id": 4,
    "name": "ddd",
    "price": 444,
    "discount": 0
  }
]