Run results for: for vs for in with index 2

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.96 Safari/537.36

Browser: Chrome 72

Operating system: Windows

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
for	40.3 Ops/sec
for..of with index	1498.5 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 };