Why can't I do array[-1] in JavaScript?

Question

In Python, you can do that:

arr = [1,2,3]
arr[-1] // evaluates to 3

But in JS, you can\'t:

let arr = [1,2,3];
arr[-1]; // e         


        

Answer 1

You miss the point, that arrays are objects (exotic object) and -1 is a valid key.

var array = [1, 2, 3];

array[-1] = 42;

console.log(array);
console.log(array[-1]);