Why the answer is 4? Could somebody explain this example, please?

Question

var arr, arr1, arr2;
arr1 = new Array(1, 0, 2);
arr2= new Array(4, 2, 0);
arr = arr2.concat(arr1);
console.log(arr[arr[2]]);

Answer 1

🤔🤷‍♂️

Answer 2

after concatenation, arr elements are [4,2,0,1,0,2] so arr[2] equals 0 because it is the third element (indexes: 0 = 4, 1 = 2, 2 = 0,...)
and arr[0] equals 4.
basically arr[ arr[2]] is equivalent to arr[0] which is 4.

Answer 3

After concat (add) gets one array:
arr = [4,2,0,1,0,2]
then inner array points to: arr[2] = 0 (we count from 0 so we get third item, which is 0)
therefore outer array: arr[0] = 4 (first item of the same array)