CODEWITHSUNDEEP
javascriptarraysecmascript-6
Mauro74
Mauro74

Reputation: 4826

Group array of objects by different keys

I have an array of objects structured as below:

const myArr = [
   { name: "John", surname: "Smith", age: 18},
   { name: "Steve", surname: "Jones", age: 23},
   { name: "Mark", surname: "Green", age: 45},
   { name: "Anne", surname: "Williams", age: 34}
]

And I would like to group it like so:

[
   {name: ["John", "Steve", "Mark", "Anne"]},
   {surname: ["Smith", "Jones", "Green", "Williams"]},
   {age: [18, 23, 45, 34]}
]

What's the best way? Tried with reduce() but no luck.

Upvotes: 0

Views: 54

Answers (4)

Siva Kondapi Venkata
Siva Kondapi Venkata

Reputation: 11001

Use forEach and build an object with keys and aggregate values in array.
Now, create the array from above object entries.

const process = (arr) => {
  const res = {};
  arr.forEach((item) =>
    Object.entries(item).forEach(([key, value]) =>
      (res[key] ??= []).push(value)
    )
  );
  return Object.entries(res).map(([key, value]) => ({ [key]: value }));
};

const myArr = [
  { name: "John", surname: "Smith", age: 18 },
  { name: "Steve", surname: "Jones", age: 23 },
  { name: "Mark", surname: "Green", age: 45 },
  { name: "Anne", surname: "Williams", age: 34 },
];

console.log(process(myArr));

Upvotes: 0

Nina Scholz
Nina Scholz

Reputation: 386578

You could iterate the array, get all entries from the object and push to the array with the wanted key.

const
    array = [{ name: "John", surname: "Smith", age: 18 }, { name: "Steve", surname: "Jones", age: 23 }, { name: "Mark", surname: "Green", age: 45 }, { name: "Anne", surname: "Williams", age: 34 }],
    result = array.reduce((r, o) => {
        Object.entries(o).forEach(([k, v]) => (r[k] ??= []).push(v));
        return r;
    }, {});

console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 1

DedaDev
DedaDev

Reputation: 5249

Nastier but shorter.

Object.keys(myArr[0]).map(key => ({ [key]: myArr.map(item => item[key]) }));

Upvotes: 1

Alexandre Senges
Alexandre Senges

Reputation: 1599

Assuming you know all objects have exactly the same keys, you can use Object.keys() function on the first element of the array, then iterate over the keys to create your objects

Object.keys(myArr[0]).map(key => {
    const obj = {}; // Probably a better way to do that
    obj[key] = myArr.map(item => item[key]);
    return obj;
});

Upvotes: 2

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