Run results for: JavaScript spread operator vs Object.assign performance with 1000 props

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36

Browser: Chrome 134

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Using the spread operator

16K/s

Using Object.assign

16K/s

View exact numbers

Test name	Executions per second
✓ Using the spread operator	16,293 Ops/sec
Using Object.assign	16,134 Ops/sec

Script Preparation code:

const firstObject = {};
const secondObject = {};

for (let i = 0; i < 1000; i++) {
  firstObject[i] = i;
  secondObject[i + 500] = i;
}

window.firstObject = firstObject;
window.secondObject = secondObject;

Tests:

Using the spread operator
const finalObject = { ...window.firstObject, ...window.secondObject };
Using Object.assign
const finalObject = Object.assign({}, window.firstObject, window.secondObject);