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

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser: Chrome 133

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Using Object.assign

3K/s

Using the spread operator

3K/s

View exact numbers

Test name	Executions per second
✓ Using Object.assign	3,487 Ops/sec
Using the spread operator	3,373 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);