JS: Print main diagonal of array using array methods

Question

How to print the main diagonale of array without using cycle for(...) but using array methods instead?

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 const arr = [
 [1,6,8,-1],
 [0,2,-6,5],
 [0,-5,3,6],
 [9,-1,1,0] ];

---

Here elements arr[0][0] = 1, arr[1][1]=2, arr[2][2]=3, arr[3][3]=0 are elements of the main diagonale. We can print them using cycle for:

---

for (let i=0;i<arr.length;i++)
{
    console.log(arr[i][i]);
}

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But is there a possibility to print them using methods .forEach .map or another one?

Answer 1

You can use Array.prototype.map but essentially they use the loops inside:

var a = [
 [1,6,8,-1],
 [0,2,-6,5],
 [0,-5,3,6],
 [9,-1,1,0] ];

var r = a.map((v, i) => v[i]);

console.log(r);