Run results for: Performance of JavaScript .forEach() vs for()

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:128.0) Gecko/20100101 Firefox/128.0

Browser: Firefox 128

Operating system: Windows

Device Platform: Desktop

Date tested: 10 months ago

.forEach

22/s

.for (init array)

20/s

View exact numbers

Test name	Executions per second
✓ .forEach	22 Ops/sec
.for (init array)	20 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;
}

Tests:

.forEach
const array = generateTestArray(); array.forEach((x) => { x.r = x.a + x.b; });
.for (init array)
const array = generateTestArray(); const r = new Array(array.length); for (let i = 0; i < array.length; ++i) { r[i] = array[i].a + array[i].b; }