从 JSON 文件中获取特定键/值对的数组答案

【问题标题】：Getting an array of specific key/value pairs from JSON file从 JSON 文件中获取特定键/值对的数组
【发布时间】：2020-11-30 14:50:38
【问题描述】：

这里是初学者 - 我想从 JSON 文件为我的世界城市类型提前项目创建一个数组。我已经获取了数据，现在我想提取 2 个键/值对（称为名称/国家/地区）并将它们推送到一个新的字符串数组中，该数组将具有以下语法：

const arr = ["name, country", "name, country", "name, country"...]

以下是数据示例：

[]:
0: {country: "Andorra", geonameid: 3040051, name: "les Escaldes", subcountry: "Escaldes-Engordany"}
1: {country: "Andorra", geonameid: 3041563, name: "Andorra la Vella", subcountry: "Andorra la Vella"}
2: {country: "United Arab Emirates", geonameid: 290594, name: "Umm al Qaywayn", subcountry: "Umm al Qaywayn"}
3: {country: "United Arab Emirates", geonameid: 291074, name: "Ras al-Khaimah", subcountry: "Raʼs al Khaymah"}...

我知道我必须使用 .push() 和 .forEach() 或 for 循环，但我不知道该怎么做。谁能告诉我怎么做？

【问题讨论】：

data.forEach(i => arr.push(i.name + ", " + i.country)) 应该这样做
@ibrahimmahrir，注意到就知道了，谢谢
data.map(i => arr.push(`${i.name} , ${i.country}`)
Demo for my comment
@AbishekKumar 你还在使用map，比如forEach。那应该是forEach 而不是map。

标签： javascript arrays json javascript-objects

【解决方案1】：

像这样使用map：

const arr = data.map(city => city.name + ", " + city.country);

arr 将是一个与data 长度相同的新数组，其中data 中的每个city 对象都映射到字符串city.name + ", " + city.country。

演示：

const data = [ {country: "Andorra", geonameid: 3040051, name: "les Escaldes", subcountry: "Escaldes-Engordany"}, {country: "Andorra", geonameid: 3041563, name: "Andorra la Vella", subcountry: "Andorra la Vella"}, {country: "United Arab Emirates", geonameid: 290594, name: "Umm al Qaywayn", subcountry: "Umm al Qaywayn"}, {country: "United Arab Emirates", geonameid: 291074, name: "Ras al-Khaimah", subcountry: "Raʼs al Khaymah"} ];

const arr = data.map(city => city.name + ", " + city.country);

console.log(arr);

【讨论】：

【解决方案2】：

const data = [{country: "Andorra", geonameid: 3040051, name: "les Escaldes", subcountry: "Escaldes-Engordany"},
{country: "Andorra", geonameid: 3041563, name: "Andorra la Vella", subcountry: "Andorra la Vella"},
{country: "United Arab Emirates", geonameid: 290594, name: "Umm al Qaywayn", subcountry: "Umm al Qaywayn"},
{country: "United Arab Emirates", geonameid: 291074, name: "Ras al-Khaimah", subcountry: "Raʼs al Khaymah"}]

const arr = data.map(i => `${i.name} , ${i.country}`);
console.log(arr)

【讨论】：

【解决方案3】：

如果你愿意，你可以使用reduce函数：

arr.reduce((acc, curr) => [...acc, (`${curr.name}, ${curr.country}`)], []);

它将以您想要的格式返回您的值。

以下示例。

const arr = [
    {country: 'Andorra', geonameid: 3040051, name: 'les 1', subcountry: 'Escaldes-Engordany'},
    {country: 'Turkey', geonameid: 3040021, name: 'les Escaldes', subcountry: 'aaaa'},
    {country: 'IDK', geonameid: 3040021, name: 'Wow', subcountry: 'aaaa'}
];
const custom = arr.reduce((acc, curr) => [...acc, (`${curr.name}, ${curr.country}`)], []);
console.log(custom);

【讨论】：

【解决方案4】：

使用 forEach 的简单解决方案

countries = [
  {country: "Andorra", geonameid: 3040051, name: "les Escaldes", subcountry: "Escaldes-Engordany"},
  {country: "Andorra", geonameid: 3041563, name: "Andorra la Vella", subcountry: "Andorra la Vella"},
  {country: "United Arab Emirates", geonameid: 290594, name: "Umm al Qaywayn", subcountry: "Umm al Qaywayn"},
  {country: "United Arab Emirates", geonameid: 291074, name: "Ras al-Khaimah", subcountry: "Raʼs al Khaymah"}
]

let arr = [];

let result = [];

countries.forEach((country, index) => {
    let nameStr = `${country.name}, ${country.country}`
    result.push(nameStr);
})

console.log(result)

//output
//["les Escaldes Andorra", "Andorra la Vella Andorra", "Umm al Qaywayn United Arab Emirates", "Ras al-Khaimah United Arab Emirates"]

【讨论】：