如何从嵌套数组创建 object 数组？

Question

I have the following array:

const a = [{
    Name: 'martha',
    Surname: 'james',
    Type: 'student',
  },
  {
    Name: 'Meredith',
    Surname: 'Napier',
    Type: 'Teacher',
  },
  {
    Name: 'Julie',
    Surname: 'Schrutt',
    Type: 'student',
  }
]

I need to convert in the following format:

const a = [{
      Type: 'student',
      Names: [{
          Firstname: 'martha',
          Lastname: 'james'
        },
        {
          Firstname: 'Julie',
          Lastname: 'schrutt'
        }
      ],
    },
    {
      Type: 'Teacher',
      Names: [{
        Firstname: 'meredith',
        Lastname: 'Napier'
      }, ],
    }

I have tried lodash grouping, object.entries, array map, reduce, but not able to figure out how to do it.

Answer 1

You can easily achieve this result using reduce in js.

 const a = [ { Name: "martha", Surname: "james", Type: "student", }, { Name: "Meredith", Surname: "Napier", Type: "Teacher", }, { Name: "Julie", Surname: "Schrutt", Type: "student", }, ]; const result = a.reduce((acc, curr) => { const { Name, Surname, Type } = curr; const elSearch = acc.find((o) => o.Type === Type); if (elSearch) { elSearch.Names.push({ Firstname: Name, Lastname: Surname, }); } else { acc.push({ Type, Names: [ { Firstname: Name, Lastname: Surname, }, ], }); } return acc; }, []); console.log(result);

You can make the above code snippet shorter if you change the name of the variable while destructuring

const { Name: Firstname, Surname: Lastname, Type } = curr;

and use it as

elSearch.Names.push({ Firstname, Lastname });

 const a = [ { Name: "martha", Surname: "james", Type: "student"}, { Name: "Meredith", Surname: "Napier", Type: "Teacher"}, { Name: "Julie", Surname: "Schrutt", Type: "student"}, ]; const result = a.reduce((acc, curr) => { const { Name: Firstname, Surname: Lastname, Type } = curr; const elSearch = acc.find((o) => o.Type === Type); if (elSearch) { elSearch.Names.push({ Firstname, Lastname }); } else { acc.push({ Type, Names: [{ Firstname, Lastname }] }); } return acc; }, []); console.log(result);

Answer 2

Using forEach :

 const a = [{ Name: 'martha', Surname: 'james', Type: 'student', }, { Name: 'Meredith', Surname: 'Napier', Type: 'Teacher', }, { Name: 'Julie', Surname: 'Schrutt', Type: 'student', } ]; const out = [{Type: 'student', Names: []}, {Type: 'teacher', Names: []}]; a.forEach(a => { if (a.Type === 'student') return out[0].Names.push({ Firstname: a.Name, Lastname: a.Surname, }); out[1].Names.push({ Firstname: a.Name, Lastname: a.Surname, }); }); console.log(out);

Answer 3

Try something like this:

const output = {};    

for(const person of array) {
    if(!output[person.Type]) output[person.Type] = { Type: person.Type, Names:[] };
    output[person.Type].Names.push({ Firstname: person.Name, Lastname: person.Surname });
}

return Object.values(output);

Or in short:

Object.values(array.reduce((pre, curr) => {
    if(!pre[curr.Type]) pre[curr.Type] = { Type: curr.Type, Names:[] };
    pre[curr.Type].Names.push({ Firstname: curr.Name, Lastname: curr.Surname });
    return pre;
} , {}))

Answer 4

 const a = [{ Name: 'martha', Surname: 'james', Type: 'student', }, { Name: 'Meredith', Surname: 'Napier', Type: 'Teacher', }, { Name: 'Julie', Surname: 'Schrutt', Type: 'student', } ] const types = a.reduce((acc, next) => { if (acc.includes(next.Type)) { return acc } return acc.concat(next.Type) }, []) const arrayByTypes = types.map((type) => { return { Type: type, Names: a.filter(item => item.Type === type).map(filtered => ({ Name: filtered.Name, Surname: filtered.Surname })) } }) console.log(arrayByTypes)

Answer 5

const data = [{
        Name: 'martha',
        Surname: 'james',
        Type: 'student',
    },
    {
        Name: 'Meredith',
        Surname: 'Napier',
        Type: 'Teacher',
    },
    {
        Name: 'Julie',
        Surname: 'Schrutt',
        Type: 'student',
    }
]

function processData(data) {
    finalMap = new Map();
    data.forEach((obj) => {
        let typeName = obj["Type"];
        let firstName = obj["Name"];
        let lastName = obj["Surname"];
        if (!finalMap[typeName]) {
            finalMap[typeName] = [];
        }
        finalMap[typeName].push({
            "Firstname": firstName,
            "LastName": lastName
        });
    });
    let result = [];
    for (const [key, value] of Object.entries(finalMap)) {
        result.push({
            "Type": key,
            "Names": value
        });
    }
    return result;

}
console.log(processData(data));

Answer 6

use this method for any group by:

 const groupBy = function (list, key) { return list.reduce((finalList, item) => { const group = (finalList[item[key]] = finalList[item[key]] || []) group.push(item) return finalList }, {}) } const a = [{ Name: 'martha', Surname: 'james', Type: 'student', }, { Name: 'Meredith', Surname: 'Napier', Type: 'Teacher', }, { Name: 'Julie', Surname: 'Schrutt', Type: 'student', } ] console.log(groupBy(a, 'Type'))

Answer 7

We can use Array.reduce & Object.values in order to achieve the expected output.

 const a = [{Name:'martha',Surname:'james',Type:'student'},{Name:'Meredith',Surname:'Napier',Type:'Teacher'},{Name:'Julie',Surname:'Schrutt',Type:'student'}]; const groupBy = (data, by) => { const result = data.reduce((acc, obj) => { const key = obj[by]; const { Type, Name: Firstname, Surname: Lastname } = obj; acc[key] = acc[key] || { Type, Names: []}; acc[key].Names.push({ Firstname, Lastname }); return acc; }, {}); return Object.values(result); } console.log(groupBy(a, "Type"));

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We can also use Logical nullish assignment (??=) instead of acc[obj[by]] = acc[obj[by]] || { Type, Names: []} acc[obj[by]] = acc[obj[by]] || { Type, Names: []}

 const a = [{Name:'martha',Surname:'james',Type:'student'},{Name:'Meredith',Surname:'Napier',Type:'Teacher'},{Name:'Julie',Surname:'Schrutt',Type:'student'}]; const groupBy = (data, by) => { const result = data.reduce((acc, obj) => { const key = obj[by]; const { Type, Name: Firstname, Surname: Lastname } = obj; acc[key]??= { Type, Names: []}; acc[key].Names.push({ Firstname, Lastname }); return acc; }, {}); return Object.values(result); } console.log(groupBy(a, "Type"));

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