如何在JavaScript中反转域名与城市的映射关系？

输入数据格式 #

const inputData = [
  {
    "domain1.com": [
      { city: "New-York" },
      { city: "Denver" },
      { city: "Las-Vegas" },
      { city: "Boston" },
    ]
  },
  {
    "domain2.com": [
      { city: "Miami" },
      { city: "Las-Vegas" },
      { city: "Boston" },
    ]
  },
  {
    "domain3.com": [
      { city: "New-York" },
      { city: "Miami" },
      { city: "Las-Vegas" },
      { city: "Chicago" },
    ]
  }
];

目标输出格式 #

{
  "New-York": [ { domain: "domain1.com" }, { domain: "domain3.com" } ],
  "Denver": [ { domain: "domain1.com" } ],
  "Las-Vegas": [ { domain: "domain1.com" }, { domain: "domain2.com" }, { domain: "domain3.com" } ],
  "Boston": [ { domain: "domain1.com" }, { domain: "domain2.com" } ],
  "Miami": [ { domain: "domain2.com" }, { domain: "domain3.com" } ],
  "Chicago": [ { domain: "domain3.com" } ]
}

实现代码 #

function transformDomainCityMap(input) {
  const result = {};
  
  input.forEach(domainObj => {
    // 提取当前域名（每个对象仅含一个域名键）
    const domain = Object.keys(domainObj)[0];
    const cities = domainObj[domain];
    
    cities.forEach(({ city }) => {
      // 若结果中无该城市键，初始化空数组
      if (!result[city]) {
        result[city] = [];
      }
      // 向对应城市数组添加域名对象
      result[city].push({ domain });
    });
  });
  
  return result;
}

// 调用函数获取转换结果
const transformedData = transformDomainCityMap(inputData);
console.log(transformedData);

代码说明 #

• 初始化空对象result存储最终转换结果
• 遍历输入数组中的每个域名对象，提取域名与对应城市列表
• 逐个处理城市：若结果对象中无该城市的键则创建空数组，再将当前域名对象加入对应数组
• 最终返回转换完成的城市-域名映射对象

内容的提问来源于stack exchange，提问作者paultje182