Run results for: JavaScript Object.assign vs for in loop

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:78.0) Gecko/20100101 Firefox/78.0

Browser: Firefox 78

Operating system: Mac OS X 10.11

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
Object.assign	1264403.5 Ops/sec
for in loop	3845248.0 Ops/sec

Tests:

Object.assign
const a = { x: 'xxx', y: 1, z: null } const b = { z: 1, u: 'uuu', v: null } Object.assign(a, b);
for in loop
const a = { x: 'xxx', y: 1, z: null } const b = { z: 1, u: 'uuu', v: null } for (let prop in b) a[prop] = b[prop];