Run results for: array.at vs polyfill vs array.length

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.6 Safari/605.1.15

Browser: Safari 17

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

at(arr, idx)

28.4M/s

arr[idx]

27.7M/s

arr.at(idx)

5.5M/s

View exact numbers

Test name	Executions per second
✓ at(arr, idx)	28,385,946 Ops/sec
arr[idx]	27,747,006 Ops/sec
arr.at(idx)	5,474,439 Ops/sec

Script Preparation code:

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];
}

Tests:

arr.at(idx)
fn1();fn1();fn1();fn1();fn1();fn1();fn1();fn1();fn1();fn1();fn1();
at(arr, idx)
fn2();fn2();fn2();fn2();fn2();fn2();fn2();fn2();fn2();fn2();fn2();
arr[idx]
fn3();fn3();fn3();fn3();fn3();fn3();fn3();fn3();fn3();fn3();fn3();