javascript - 如何按属性聚合嵌套的 JavaScript 对象？

Question

我有以下 JavaScript 对象:

var example = [{
    country: "US",
    things: {
      weather: 'cloudy'
    }
  },
  {
    country: "US",
    things: {
      resource: 'lead',
      weather: 'sunny'
    }
  },
  {
    country: "MX",
    things: {
      weather: 'sunny'
    }
  },
  {
    country: "MX",
    things: {
      resource: 'gold',
      weather: 'sunny'
    }
  },
  {
    country: "MX",
    things: {
      resource: 'copper'
    }
  },
]

我想通过聚合转换成这种格式。

var out = [{
    country_code: 'US',
    things: {
      resource: ['lead'],
      weather: ['cloudy', 'sunny']
    }
  },
  {
    country_code: 'MX',
    things: {
      resource: ['gold', 'copper'],
      weather: ['sunny'],
    }
  }

]

我曾尝试研究使用 reduce 和 map 的组合，但无济于事。如果这个示例也可以作为数据操作的一般策略的起点，那么可能会或可能不会涉及数组方法的使用。

Answer 1

使用reduce 迭代对象来编译你的新对象，拼凑你想要的东西:

const example = [{
    country: "US",
    things: {
      weather: 'cloudy'
    }
  },
  {
    country: "US",
    things: {
      resource: 'lead',
      weather: 'sunny'
    }
  },
  {
    country: "MX",
    things: {
      weather: 'sunny'
    }
  },
  {
    country: "MX",
    things: {
      resource: 'gold',
      weather: 'sunny'
    }
  },
  {
    country: "MX",
    things: {
      resource: 'copper'
    }
  },
]

const out = Object.values(
  example.reduce((a, v) => {
    if (!a[v.country]) {
      a[v.country] = {
        country_code: v.country,
        things: {}
      }
    }

    Object.entries(v.things).forEach(([key, value]) => {
      if (!a[v.country].things[key]) {
        a[v.country].things[key] = []
      }

      if (!a[v.country].things[key].includes(value)) {
        a[v.country].things[key].push(value)
      }
    })

    return a
  }, {})
)

console.log(out)