const arr = new Array(512).fill(0).map(() => Math.round(Math.random() * 512));

const at = (arr, idx) => arr[(idx < 0 ? arr.length + idx : idx)];

for (let i = 0; i < arr.length; i++) arr[i] += 1; // access all elements first to allow browser engine optimization if any.

fn1();

fn2();

fn3();

​

function fn1() {

    arr.at(5);

    arr.at(2);

    arr.at(50);

    arr.at(20);

    arr.at(500);

    arr.at(200);

    arr.at(-1);

}

​

function fn2() {

    at(arr, 5);

    at(arr, 2);

    at(arr, 50);

    at(arr, 20);

    at(arr, 500);

    at(arr, 200);

    at(arr, -1);

}

​

function fn3() {

    arr[5];

    arr[2];

    arr[50];

    arr[20];

    arr[500];

    arr[200];

    arr[arr.length - 1];

}