Run results for: Spread vs Object.assign

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.2 Safari/605.1.15

Browser: Safari 18

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Object.assign two objects

173K/s

Spread two objects

165K/s

Object.assign three objects

102K/s

Spread three objects

99K/s

Object.assign four objects

85K/s

Spread four objects

79K/s

Object.assign five objects

71K/s

Spread five objects

64K/s

Object.assign six objects

52K/s

Spread six objects

44K/s

View exact numbers

Test name	Executions per second
✓ Object.assign two objects	173,248 Ops/sec
Spread two objects	165,441 Ops/sec
Object.assign three objects	102,303 Ops/sec
Spread three objects	98,791 Ops/sec
Object.assign four objects	85,061 Ops/sec
Spread four objects	78,689 Ops/sec
Object.assign five objects	71,061 Ops/sec
Spread five objects	64,164 Ops/sec
Object.assign six objects	52,293 Ops/sec
Spread six objects	44,482 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};