根据已有数据获取新内容 .map .find

const goods = [
      {id:1,name:"香蕉",price:9.9,num:150,usedata:7,data:"2019:03:20"},
      {id:2,name:"苹果",price:14,num:200,usedata:10,data:"2019:03:20"},
      {id:3,name:"血橙",price:8.9,num:350,usedata:15,data:"2019:03:20"},
      {id:4,name:"库尔勒香梨",price:11.9,num:100,usedata:7,data:"2019:03:20"},
      {id:5,name:"雪莲果",price:4.6,num:550,usedata:20,data:"2019:03:20"},
      {id:6,name:"蓝莓",price:15,num:55,usedata:7,data:"2019:03:20"},
      {id:7,name:"牛油果",price:24.6,num:35,usedata:20,data:"2019:03:20"},
    ]  

    const items = [
      {
        id:3,inventory:1
      },{
        id:6,inventory:2
      }
    ]

    const arr = items.map(item => {   // .map
      const {id,inventory} = item  //解构
      const good = goods.find(good => good.id === id)    //.find
      return {
        id,
        name:good.name,
        price:good.price,
        usedata:good.usedata,
        data:good.data,
        inventory
      }
    })
    console.log(arr)
      /* Array(2)
        0: {id: 3, name: "血橙", price: 8.9, usedata: 15, data: "2019:03:20", …}
        1: {id: 6, name: "蓝莓", price: 15, usedata: 7, data: "2019:03:20", …}
        length: 2 */

总价计算

/* let total = 0
    for (var i = 0; i < arr.length; i++) {
      total += arr[i].price * arr[i].inventory
    }
    console.log(total) */
 
const total = arr.reduce((sum,product) => sum + product.price * product.inventory,0)
    console.log(total) //38.9