Why the ouput of this code is 40?

Question

Why the output of this code is 40? Can someone explain it to me. thanks

var arrTest = [10, 20, 30, 40, 50] [1, 3];
console.log(arrTest);

Answer 1

Because the index of 40 is 3

Answer 2

It's the same as

var arrTest = [10, 20, 30, 40, 50] [3];
console.log(arrTest);
or
var arrTest = [10, 20, 30, 40, 50];
console.log(arrTest[3]);

Only the last index will be used with comma separated indexes, so, the 1 is ignored.

Answer 3

No, indices are 0 based.
0 1 2 3 4
[10, 20, 30, 40, 50]

Answer 4

Why not index 30 is 3 ?

edit : is it because index starts from 0 ?

Answer 5

Munawirul Hadi

In few Programming Language index start from 1 but in mostly language index start from 0.

Answer 6

Counting start from 0, not from 1