如何基于相同的值合并对象数组？

Question

I have this array of Objects:

var array = [{
    country: "Austria",
    name: "2019-01-04T23:00:00.000Z",
    value: "1"
  },
  {
    country: "Austria",
    name: "2019-01-11T23:00:00.000Z",
    value: "3"
  },
  {
    country: "Austria",
    name: "2019-01-18T23:00:00.000Z",
    value: "1"
  }
]

I want manipulate this to achieve this result:

var array = [{
  country: "Austria",
  series: [{
      name: "2019-01-04T23:00:00.000Z",
      value: "1"
    },
    {
      name: "2019-01-11T23:00:00.000Z",
      value: "3"
    },
    {
      name: "2019-01-18T23:00:00.000Z",
      value: "1"
    }
  ]
}]

I read many questions but none helped me.

Answer 1

This should do:

var map = {};

for(var entity of array) {
    if(!map[entity.country]) {
        map[entity.country] = {
            country: entity.country,
            series: [
                {
                    name: entity.name,
                    value: entity.value
                }
            ]
        };
    }
    else {
        map[entity.country].series.push({
            name: entity.name,
            value: entity.value            
        });
    }
}

var mappedArray = Object.values(map);

Answer 2

Here is functional solution without for loops and mutable variables:

const result = array.reduce((carry, item) => {
    if (!carry.includes(item.country)) {
        carry.push(item.country);
    }
    return carry;
}, []).map(country => {
    return {
        country: country,
        series: array.filter(item => item.country === country).map(item => {
            return {
                name: item.name,
                value: item.value
            };
        })
    };

Answer 3

You could loop thorugh the array. Use destructuring to get country and rest of the properties separately. Add each unique country to group object as key and push the rest object to the series array. Then use Object.values() to get the values as an array

 const array=[{country:"Austria",name:"2019-01-04T23:00:00.000Z",value:"1"},{country:"Austria",name:"2019-01-11T23:00:00.000Z",value:"3"},{country:"Austria",name:"2019-01-18T23:00:00.000Z",value:"1"}]; const group = {}; array.forEach(({ country, ...rest }) => { group[country] = group[country] || { country, series: [] }; group[country].series.push(rest) }) console.log(Object.values(group)) 

Answer 4

You can do something like:

const result = array
    .map(
        c => ({
            country: c.country,
            series: array
                .filter(d => d.country === c.country)
                .map(
                    d => ({
                        name: d.name,
                        value: d.value
                    })
                )
        })
    )