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

Question

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.

Accepted Answer

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.