Run results for: Spread vs Object.assign (mutation)

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 Edg/134.0.0.0

Browser: Chrome 134

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Object.assign two objects

185K/s

Object.assign three objects

89K/s

Object.assign four objects

56K/s

Spread two objects

41K/s

Object.assign five objects

39K/s

Object.assign six objects

34K/s

Spread three objects

22K/s

Spread four objects

14K/s

Spread five objects

11K/s

Spread six objects

9K/s

View exact numbers

Test name	Executions per second
✓ Object.assign two objects	184,919 Ops/sec
Object.assign three objects	88,900 Ops/sec
Object.assign four objects	56,413 Ops/sec
Spread two objects	41,400 Ops/sec
Object.assign five objects	39,123 Ops/sec
Object.assign six objects	34,141 Ops/sec
Spread three objects	21,848 Ops/sec
Spread four objects	14,499 Ops/sec
Spread five objects	10,829 Ops/sec
Spread six objects	8,738 Ops/sec

Script Preparation code:

window.object1 = {};
window.object2 = {};
window.object3 = {};
window.object4 = {};
window.object5 = {};
window.object6 = {};

function makeid() {
  var text = "";
  var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

  for (var i = 0; i < 5; i++)
    text += possible.charAt(Math.floor(Math.random() * possible.length));

  return text;
};

function populate(object) {
  for (let i = 0; i < 100; i++) {
    object[makeid()] = makeid();
  }
};

populate(object1);
populate(object2);
populate(object3);
populate(object4);
populate(object5);
populate(object6);

Tests:

Object.assign two objects
const object7 = Object.assign(object1, object2);
Spread two objects
const object7 = {...object1, ...object2};
Object.assign three objects
const object7 = Object.assign(object1, object2, object3);
Spread three objects
const object7 = {...object1, ...object2, ...object3};
Object.assign four objects
const object7 = Object.assign(object1, object2, object3, object4);
Spread four objects
const object7 = {...object1, ...object2, ...object3, ...object4};
Object.assign five objects
const object7 = Object.assign(object1, object2, object3, object4, object5);
Spread five objects
const object7 = {...object1, ...object2, ...object3, ...object4, ...object5};
Object.assign six objects
const object7 = Object.assign(object1, object2, object3, object4, object5, object6);
Spread six objects
const object7 = {...object1, ...object2, ...object3, ...object4, ...object5, ...object6};