Question

我试图将对象数组转换为hashmap。我只有部分ES6可用，我也不能使用Map。

数组中的对象非常简单，例如{nation: {name: string, iso: string, scoringPoints: number}。我需要按scoringPoints对它们进行排序。我现在想要一本＆＃34;字典＆＃34;通过iso保持等级 - > {[iso:string]:number}。

我已经尝试过（来自here (SO)）

const dict = sortedData.reduce((prev, curr, index, array) => (
    { ...array, [curr.nation.iso]: ++index }
), {});

但dict原来是Object，其索引以0开头。希望我能看到一件小事。但目前我的头脑是旋转如何将一个简单的数组转换为类似hashmap的对象。也许Array.map？

我还应该注意到我正在使用TypeScript，在没有正确输入之前我也遇到了一些麻烦。

const test = [
    { nation: { name: "Germany", iso: "DE", rankingPoints: 293949 } },
    { nation: { name: "Hungary", iso: "HU", rankingPoints: 564161 } },
    { nation: { name: "Serbia", iso: "SR", rankingPoints: 231651 } }
];

const sorted = test.sort((a, b) => a.nation.rankingPoints - b.nation.rankingPoints);
const dict = sorted.reduce((prev, curr, index, array) => ({ ...array, [curr.nation.iso]: ++index }), {});
console.log(JSON.stringify(dict));

正在显示

{
    "0": {
        "nation": {
            "name": "Serbia",
            "iso": "RS",
            "rankingPoints": 231651
        }
    },
    "1": {
        "nation": {
            "name": "Germany",
            "iso": "DE",
            "rankingPoints": 293949
        }
    },
    "2": {
        "nation": {
            "name": "Hungary",
            "iso": "HU",
            "rankingPoints": 564161
        }
    },
    "HU": 3
}

在控制台中。

根据评论，我想要的是像

这样的类似hashmap的对象

{
    "HU": 1,
    "DE": 2,
    "RS": 3
}

其中属性值是排序数据中的排名（+1），因此我可以通过访问dict["DE"]来获取排名2。

Answer 1

使用forEach或reduce

捕获数据中每个键的位置

const test = [
    { nation: { name: "Germany", iso: "DE", rankingPoints: 293949 } },
    { nation: { name: "Hungary", iso: "HU", rankingPoints: 564161 } },
    { nation: { name: "Serbia", iso: "SR", rankingPoints: 231651 } }
];    

const sorted = test.sort((a, b) => a.nation.rankingPoints - b.nation.rankingPoints);

// Using forEach:

var dict = {}
sorted.forEach((el, index) => dict[el.nation.iso] = sorted.length - index);

// Using reduce:

dict = sorted.reduce(
    (dict, el, index) => (dict[el.nation.iso] = sorted.length - index, dict),
    {}
);

console.log(dict)
console.log("dict['DE'] = ", dict['DE'])

输出：

{
  "SR": 3,
  "DE": 2,
  "HU": 1
}
dict['DE'] =  2

（注意，在用作地图的对象中，属性的顺序并不重要 - 如果您需要特定的顺序，请使用数组。）

Answer 2

const test = [
  { nation: { name: "Germany", iso: "DE", rankingPoints: 293949 } },
  { nation: { name: "Hungary", iso: "HU", rankingPoints: 564161 } },
  { nation: { name: "Serbia", iso: "SR", rankingPoints: 231651 } }
];

const sorted = test.sort((a, b) =>  b.nation.rankingPoints - a.nation.rankingPoints);
const dict = sorted.reduce((result, curr, index, array) => ({ ...result, [curr.nation.iso]: ++index }), {});
console.log(JSON.stringify(dict));

Answer 3

也可以使用 Array.map 和 Object.fromEntries 来实现：

const test = [
  { nation: { name: "Germany", iso: "DE", rankingPoints: 293949 } },
  { nation: { name: "Hungary", iso: "HU", rankingPoints: 564161 } },
  { nation: { name: "Serbia", iso: "SR", rankingPoints: 231651 } }
];

const sorted = test.sort((a, b) => a.nation.rankingPoints < b.nation.rankingPoints ? 1 : (a.nation.rankingPoints > b.nation.rankingPoints ? -1 : 0));

const dict = Object.fromEntries(sorted.map((c, index) => [c.nation.iso, index + 1]));

console.log(dict);

将js Array转换为Dictionary / Hashmap

3 个答案: