对对象数组中的两个值求和，然后插入到另一个对象数组中

Question

我有一个名为 stores 的对象数组：

stores = [
{
storeId: 1,
city: "San Francisco",
state: "CA",
},
{
storeId: 2,
city: "Seattle",
state: "WA",
},
{
storeId: 3,
city: "Vancouver",
state: "BC",
},
{
storeId: 4,
city: "Los Angeles",
state: "CA",
},
]

以及另一个称为 items 的对象数组：

items = [
{
itemId: 1,
cost: 10,
price: 20,
sold: false,
_storeId: 1,
},
{
itemId: 2,
cost: 10,
price: 20,
sold: false,
_storeId: 1,
},
{
itemId: 3,
cost: 5,
price: 12,
sold: true,
_storeId: 2,
},
{
itemId: 4,
cost: 12,
price: 20,
sold: false,
_storeId: 3,
},
{
itemId: 5,
cost: 2,
price: 10,
sold: false,
_storeId: 4,
},
{
itemId: 6,
cost: 10,
price: 50,
sold: true,
_storeId: 4,
},
]

我想按商店对以下类别进行汇总：

• 总成本
• 总价

然后按商店计算总商品数：

• 总项目

然后计算商店销售的小计商品：

• 已售出商品

所以我的最终存储数组看起来像这样：

storesUpdated = [
{
storeId: 1,
city: "San Francisco",
state: "CA",
totalCost: 20,
totalPrice: 40,
countTotalItems: 2,
countSoldItems: 0
},
{
storeId: 2,
city: "Seattle",
state: "WA",
totalCost: 5,
totalPrice: 12,
countTotalItems: 1,
countSoldItems: 1
},
{
storeId: 3,
city: "Vancouver",
state: "BC",
totalCost: 12,
totalPrice: 20,
countTotalItems: 1,
countSoldItems: 0
},
{
storeId: 4,
city: "Los Angeles",
state: "CA",
totalCost: 12,
totalPrice: 60,
countTotalItems: 2,
countSoldItems: 1
},
]

我尝试在商店阵列上映射，但卡在这里：

const storesUpdated = stores.map((store) => {
= {}
items.forEach(item => {
if (item._storeId === store.storeId) {
return totalCost {
'storeId' : item.storeId,
}
}
})
})

有什么想法吗？非常感谢。

Answer 1

const stores = [{storeId:1,city:"San Francisco",state:"CA",},{storeId:2,city:"Seattle",state:"WA",},{storeId:3,city:"Vancouver",state:"BC",},{storeId:4,city:"Los Angeles",state:"CA",},]
const items = [{itemId:1,cost:10,price:20,sold:!1,_storeId:1,},{itemId:2,cost:10,price:20,sold:!1,_storeId:1,},{itemId:3,cost:5,price:12,sold:!0,_storeId:2,},{itemId:4,cost:12,price:20,sold:!1,_storeId:3,},{itemId:5,cost:2,price:10,sold:!1,_storeId:4,},{itemId:6,cost:10,price:50,sold:!0,_storeId:4,},]
const storesUpdated = stores.map((store) => {
const updatedStore = { ...store,
totalCost: 0,
totalPrice: 0,
countTotalItems: 0,
countSoldItems: 0
}

items.forEach(item => {
if (item._storeId === store.storeId) {
updatedStore.totalCost += item.cost
updatedStore.totalPrice += item.price
updatedStore.countTotalItems += 1
updatedStore.countSoldItems += item.sold ? 1 : 0
}
})

return updatedStore
})
console.log(storesUpdated)

Answer 2

如果只想遍历一次数据，可以通过两个步骤执行合并：

• 创建"空"存储并在单个reduce中按id索引它们：(一个循环stores(

  const Store = (data) => ({ /* ... */ });
  const storesById = storeData => storeData.reduce(
  (map, sd) => Object.assign(map, { [sd.storeId]: Store(sd) }),
  {}
  );
  

• 循环访问项目并将它们合并到相应的存储中：(一个循环items(

  const addItemToStoreMap = (storeMap, item) => ({
  ...storeMap,
  [item._storeId]: addItemToStore(storeMap[item._storeId], item)
  });
  

请注意，使用对象传播语法创建所有新对象会抵消性能提升，但这是 O(n + m( 而不是 O(n * m( 仍然很好。

把所有的东西放在一起：

const storeData = [{storeId:1,city:"San Francisco",state:"CA",},{storeId:2,city:"Seattle",state:"WA",},{storeId:3,city:"Vancouver",state:"BC",},{storeId:4,city:"Los Angeles",state:"CA",},]
const itemData = [{itemId:1,cost:10,price:20,sold:!1,_storeId:1,},{itemId:2,cost:10,price:20,sold:!1,_storeId:1,},{itemId:3,cost:5,price:12,sold:!0,_storeId:2,},{itemId:4,cost:12,price:20,sold:!1,_storeId:3,},{itemId:5,cost:2,price:10,sold:!1,_storeId:4,},{itemId:6,cost:10,price:50,sold:!0,_storeId:4,},]
const { Store, addItemToStoreMap, storesById } = storeUtils();
// Loop over the stores *once*, loop over the items *once*
// During the second loop, add items to the right stores
const itemsByStoreId = itemData.reduce(addItemToStoreMap, storesById(storeData));
console.log(Object.values(itemsByStoreId));
function storeUtils() {
// Our client-side model for a Store
const Store = ({ storeId, city, state }) => ({
storeId,
city,
state,
totalCost: 0,
totalPrice: 0,
countTotalItems: 0,
countSoldItems: 0
});
// Merge logic for adding an item to a store
// Can be used in a reduce on a list of items seeded with a store
const addItemToStore = (store, item) => ({
...store,
totalCost: store.totalCost + item.cost,
totalPrice: store.totalPrice + item.price,
countTotalItems: store.countTotalItems + 1,
countSoldItems: store.countSoldItems + item.sold
});
// Selects the right store for an item and returns a new
// map with the updated store
const addItemToStoreMap = (storeMap, item) => ({
...storeMap,
[item._storeId]: addItemToStore(storeMap[item._storeId], item)
});
// Converts raw data to Store objects and indexes them by their id
const storesById = storeData => storeData.reduce(
(map, sd) => Object.assign(map, { [sd.storeId]: Store(sd) }),
{}
);
return { Store, addItemToStoreMap, storesById };
};