javascript - 如何用另一个对象的键更改对象的键

Question

我被困在将对象结果的键更改为另一个对象的另一个键，也许我的代码不是动态的，我确实喜欢从这里的人们那里得到一些提示:

function country(arr) {
  var obj = {},
    temp = {}
  for (i of arr) {
    if (i.length === 2) {
      if (!temp[i[0]])
        temp[i[0]] = []
      temp[i[0]].push(i[1])
    }

    if (i.length === 3) {
      obj[i[2]] = []
    }

  }
  console.log(obj) // final result
  console.log(temp)

}

var cities = [
  ["c", "br", "Brazil"],
  ["br", "Rio de Jeneiro"],
  ["c", "usa", "United States"],
  ["ru", "St. Petersburg"],
  ["usa", "New York"],
  ["ksa", "Mekkah"],
  ["usa", "Washington DC"],
  ["usa", "California"],
  ["c", "ch", "China"],
  ["ksa", "Madinah"],
  ["ch", "Beijing"],
  ["c", "ind", "India"],
  ["ch", "Shanghai"],
  ["ind", "Bangalore"],
  ["ind", "New Delhi"],
  ["c", "ru", "Rusia"],
  ["ru", "Moscow"],
  ["c", "ksa", "Arab Saudi"]
]

console.log(country(cities))

变量obj是我想要输出的键，

所以我想要的输出是这样的:

{
      Brazil: [ 'Rio de Jeneiro' ],
      'United States': [ 'New York', 'Washington DC', 'California' ],
     ............ rest...
}

是否可以将 temp 对象的键 obj 更改为变量 obj 中的键？？

Answer 1

下面使用一些数组方法，即 filter、map 和 forEach，根据请求格式化数据。

var cities = [
  ["c", "br", "Brazil"],
  ["br", "Rio de Jeneiro"],
  ["c", "usa", "United States"],
  ["ru", "St. Petersburg"],
  ["usa", "New York"],
  ["ksa", "Mekkah"],
  ["usa", "Washington DC"],
  ["usa", "California"],
  ["c", "ch", "China"],
  ["ksa", "Madinah"],
  ["ch", "Beijing"],
  ["c", "ind", "India"],
  ["ch", "Shanghai"],
  ["ind", "Bangalore"],
  ["ind", "New Delhi"],
  ["c", "ru", "Rusia"],
  ["ru", "Moscow"],
  ["c", "ksa", "Arab Saudi"]
]

let lookup = {};

cities.filter(city => city[0] === "c").forEach(country => {
  let matches = cities
    .filter(city => city[0] === country[1])
    .map(city => city[1]);
  lookup[country[2]] = matches;
});

console.log(lookup);

编辑:这是一个不使用数组函数的解决方案。

var cities = [
  ["c", "br", "Brazil"],
  ["br", "Rio de Jeneiro"],
  ["c", "usa", "United States"],
  ["ru", "St. Petersburg"],
  ["usa", "New York"],
  ["ksa", "Mekkah"],
  ["usa", "Washington DC"],
  ["usa", "California"],
  ["c", "ch", "China"],
  ["ksa", "Madinah"],
  ["ch", "Beijing"],
  ["c", "ind", "India"],
  ["ch", "Shanghai"],
  ["ind", "Bangalore"],
  ["ind", "New Delhi"],
  ["c", "ru", "Rusia"],
  ["ru", "Moscow"],
  ["c", "ksa", "Arab Saudi"]
];

let lookup = {};

for (let i = 0; i < cities.length; i++) {
  // Test if this is a country
  if (cities[i][0] === "c") {
    // Make sure we have not processed this country before
    if (!lookup[cities[i][2]]) {
      lookup[cities[i][2]] = [];
      
      let countryCode = cities[i][1];
      // Loop through cities again and match country code
      for (let j = 0; j < cities.length; j++) {
        if (cities[j][0] === countryCode) {
          lookup[cities[i][2]].push(cities[j][1]);
        }
      }
    }
  }
}

console.log(lookup);