Run results for: Spread vs Object.assign mutate

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser: Chrome 131

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Object.assign two objects

48K/s

Spread two objects

45K/s

View exact numbers

Test name	Executions per second
✓ Object.assign two objects	47,613 Ops/sec
Spread two objects	44,887 Ops/sec

Script Preparation code:

window.object1 = {};
window.object2 = {};

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);

Tests:

Object.assign two objects
let object7 = Object.assign({}, object1); object7 = Object.assign(object7, object2);
Spread two objects
const object7 = Object.assign({}, object1); const object8 = {...object7, ...object2};