如何在JavaScript中重置和更新对象值

Question

-你好！我有一个目标，我试着根据他们在一年(国内生产总值) GDP中产生的货币数量来分类，同时更新这个名为“排名”的属性，从最高到最低。

const countryData = [
  { rank: 5, name: "Norway", gpd: 77975.4 },
  { rank: 3, name: "Macao", gpd: 81151.9 },
  { rank: 4, name: "Ireland", gpd: 77771.2 },
  { rank: 2, name: "Luxembourg", gpd: 113196.5 },
  { rank: 6, name: "Qatar", gpd: 69687.7 },
  { rank: 1, name: "Switzerland", gpd: 83716.8 },
];

输出应该如下所示：

const countryData = [
  { rank: 1, name: "Luxembourg", gpd: 113196.5 },
  { rank: 2, name: "Switzerland", gpd: 83716.8 },
  { rank: 3, name: "Macao", gpd: 81151.9 },
  { rank: 4, name: "Norway", gpd: 77975.4 },
  { rank: 5, name: "Ireland", gpd: 77771.2 },
  { rank: 6, name: "Qatar", gpd: 69687.7 },
]; 

我一直在使用sort()方法，如下所示：

const orderer = countryData.sort((a,b) => 
  a.gpd < b.gpd ? 1 : -1);
  console.log(orderer);

而且起作用了！但我不知道如何重置和更新排名，我知道应该使用map()方法或for循环。

提前感谢！

Answer 1

对数据进行排序之后，循环遍历数组并重新分配级别。

​

const countryData = [
  { rank: 5, name: "Norway", gpd: 77975.4 },
  { rank: 3, name: "Macao", gpd: 81151.9 },
  { rank: 4, name: "Ireland", gpd: 77771.2 },
  { rank: 2, name: "Luxembourg", gpd: 113196.5 },
  { rank: 6, name: "Qatar", gpd: 69687.7 },
  { rank: 1, name: "Switzerland", gpd: 83716.8 },
];

const orderer = countryData.sort((a,b) => 
  a.gpd < b.gpd ? 1 : -1);

orderer.forEach((o, i) => o.rank = i+1);
console.log(orderer);

​

Answer 2

也许像这样？

const countryData = [
  { rank: 5, name: "Norway", gpd: 77975.4 },
  { rank: 3, name: "Macao", gpd: 81151.9 },
  { rank: 4, name: "Ireland", gpd: 77771.2 },
  { rank: 2, name: "Luxembourg", gpd: 113196.5 },
  { rank: 6, name: "Qatar", gpd: 69687.7 },
  { rank: 1, name: "Switzerland", gpd: 83716.8 }
]

// Name every function to make it testable
// (maybe later, but...):
const by = prop => (a, b) => a[prop] < b[prop] ? 1 : -1
const update = rank => (o, i) => Object.assign({}, o, o[rank] = ++i)

// Now you can do that task in universal,
// testable and readable way:
const ordered = countryData
  .sort(by('gpd'))
  .map(update('rank'))

console.log(ordered)

Answer 3

这是Y的解决方案。它看起来更干净：

let countryDataUpdate = countryData;
countryDataUpdate.sort((a,b) => a.gpd < b.gpd ? 1 : -1)
.map((value, index) => {
  value.rank = index + 1;
  return value;
});