How can I group an array with nested array?

Question

Does anyone know a simple way to group an array with nested array? For example, i have an array of animals:

[
  ['Cat', 'Dog', 'Monkey'],
  ['my pet', 'it is animals', 'terrestrial animals']
]

I want to make new array with format that's grouped by ['Cat', 'Dog', 'Monkey']:

[
  {
    groupTitle: 'Cat',
    relations: ['my pet', 'it is animals', 'terrestrial animals']
  },
  {
    groupTitle: 'Dog',
    relations: ['my pet', 'it is animals', 'terrestrial animals']
  },
  {
    groupTitle: 'Monkey',
    relations: ['my pet', 'it is animals', 'terrestrial animals']
  }
]

How can i do it? Thanks!

deekeh · Accepted Answer · 2022-01-17 07:31:17Z

4

Using `map()`

const arr = [
  ['Cat', 'Dog', 'Monkey'],
  ['my pet', 'it is animals', 'terrestrial animals']
]; // original data
const [groupTitles, relations] = arr; // array destructuring to get individual sub-arrays

const result = groupTitles.map(groupTitle => ({
  groupTitle,
  relations
}));

console.log(result); // print result

I used the following approach to achieve your desired outcome.

Use Array destructuring to get the individual arrays from the original array.
map() through the animals array to get the desired array of objects and store it in a result variable.

Using `reduce()`

const arr = [
  ['Cat', 'Dog', 'Monkey'],
  ['my pet', 'it is animals', 'terrestrial animals'],
]; // original array

const result = arr[0].reduce((a, b) => {
  return [
    ...a, // previously calculated values
    { // new value
      groupTitle: b,
      relations: arr[1],
    },
  ];
}, []);

console.log(result); // print result

The same result can also be achieved using reduce() method as required.

edited Jan 17, 2022 at 7:31

answered Jan 16, 2022 at 8:08

deekeh

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9 Comments

deekeh Over a year ago

I can't think of a way to do it with a reduce() at this moment. It seems you are actually "expanding" the array to achieve the result. Feel free to add to the answer if you get a way to it though.

deekeh Over a year ago

Not a problem! On a lighter note, I guess the down-votes for this post might be because you did not mention any work you tried yourself and got stuck. The SO community is kind of strict when it comes to asking a good question.

A Little Girl Over a year ago

I will take note of this!

Gass Over a year ago

@ALittleGirl why the interest of doing it with reduce() ?

deekeh Over a year ago

@Gass yes. Even though using reduce() is possible, I don't think reduce() fits in this use-case since we are not reducing it to a smaller product of the original array.

|

karim_mo · Accepted Answer · 2022-01-16 08:18:22Z

2

You can make a nested iteration using for loop for example:

const arr = [
  ["Cat", "Dog", "Monkey"],
  ["my pet", "it is animals", "terrestrial animals"],
];

let newArr = [];

for (let i = 0; i <= arr.length; i++) {
  for (let j = 0; j < arr[0].length; j++) {}
  newArr.push({ groupTitle: arr[0][i], relations: arr[1] });
}

console.log(newArr);

answered Jan 16, 2022 at 8:18

karim_mo

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Comments

Gass · Accepted Answer · 2022-01-16 08:27:27Z

2

Using destructuring assignments

const arr = [
  ['Cat', 'Dog', 'Monkey'],
  ['my pet', 'it is animals', 'terrestrial animals']
]

let a,b,c, obj, newArr = [];

[a,b,c] =  arr[1]

arr[0].forEach(el => {

  obj = {
    groupTitle: el,
    relations: [a,b,c]
  }
  newArr.push(obj)
})

console.log(newArr)

answered Jan 16, 2022 at 8:27

Gass

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