Run results for: for vs for in with index 2

Run details:

User agent: Mozilla/5.0 (Linux; Android 11; M2002J9G) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.66 Mobile Safari/537.36

Browser: Chrome Mobile 90

Operating system: Android

Device Platform: Mobile

Date tested: 3 years ago

Test name	Executions per second
for	28.3 Ops/sec
for..of with index	1539.3 Ops/sec

Script Preparation code:

var arr = [];

for (let i = 0; i < 100000; i++)
{
  arr[i] = i*2;
}

Tests:

for
const length = arr.length; for (let i = 0; i < length; i++) { arr[i] = arr[i]*2; }
for..of with index
let index = -1; for (let i of arr) { index++; i = i*2 };