How to make new array or arrays with contents from other arrays?

Question

First array:

const arr1 = [[1, 2, 3, 4], [5, 6, 7, 8]];

Second array:

const arr2 = [['some1', 'some2'], ['some3', 'some4']];

Desired array:

const finalArr = [[1, 2, 3, 4], ['some1', 'some2'], ['some3', 'some4']];

So, basically finalArr should have first index array of arr1 and the rest of arr2.

How can this be done?

`const finalArr = [arr1[0], ...arr2]` this should to the trick. — Ankit, Nov 15 '19 at 09:35
I can just talk for myself, and for me the reason was that the question lacks - what was already tried and what didn't work. — Ankit, Nov 15 '19 at 09:43
You can read [this](https://stackoverflow.com/questions/1584370/how-to-merge-two-arrays-in-javascript-and-de-duplicate-items) — Karmidzhanov, Nov 15 '19 at 09:48

score 4 · Accepted Answer · answered Nov 15 '19 at 09:38

If you do not care about destroying arr2, neither about having a deep copy of arr1[0], a simple unshift() can do that:

const arr1 = [[1, 2, 3, 4], [5, 6, 7, 8]];
const arr2 = [['some1', 'some2'], ['some3', 'some4']];

arr2.unshift(arr1[0]);
console.log(JSON.stringify(arr2));

Of course those are really some conditions which may not fit your case.

Sohail Ashraf · Answer 2 · 2019-11-15T09:42:28.827

1

Use ES6 spread operator as below.

const arr1 = [[1, 2, 3, 4], [5, 6, 7, 8]];

const arr2 = [['some1', 'some2'], ['some3', 'some4']];

const finalArr = [arr1[0], ...arr2];

console.log(finalArr);

Or use concat function.

const arr1 = [[1, 2, 3, 4], [5, 6, 7, 8]];
const arr2 = [['some1', 'some2'], ['some3', 'some4']];
const finalArr = [arr1[0]].concat(arr2);

console.log(finalArr);

edited Nov 15 '19 at 09:42

answered Nov 15 '19 at 09:35

Sohail Ashraf

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score -3 · Answer 3 · answered Nov 15 '19 at 09:37

const arr1 = [[1, 2, 3, 4], [5, 6, 7, 8]];

const arr2 = [['some1', 'some2'], ['some3', 'some4']];
cont finalArr = Array();
finalArr.push(arr1[0]);
finalArr.push(arr2[0]);
finalArr.push(arr2[1]);

You can also iterate through the arrays and push them dynamically.

How to make new array or arrays with contents from other arrays?

3 Answers3