Run results for: for vs foreach vs for..of with sum

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:135.0) Gecko/20100101 Firefox/135.0

Browser: Firefox 135

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

for

166/s

for..of with reassign

91/s

foreach

88/s

for..of with no reassign

40/s

View exact numbers

Test name	Executions per second
✓ for	166 Ops/sec
for..of with reassign	91 Ops/sec
foreach	88 Ops/sec
for..of with no reassign	40 Ops/sec

Script Preparation code:

function generateTestArray() {
  const result = [];
  for (let i = 0; i < 1000000; ++i) {
    result.push({
      a: i,
      b: i / 2,
      r: 0,
    });
  }
  return result;
}

const array = generateTestArray();

Tests:

for
for (let i = 0; i < array.length; i++) { array[i].r = array[i].a + array[i].b; }
foreach
sum = x => x.r = x.a + x.b; array.forEach(sum);
for..of with reassign
for (let x of array) { x.r = x.a + x.b; }
for..of with no reassign
const result = []; for (let x of array) { result.push(x.a + x.b); }

Run results for: for vs foreach vs for..of with sum

Compare loop performance

for

foreach

for..of with reassign

for..of with no reassign