Run results for: Shallow cloning an object: Object.assign() vs. Spread vs. for-in loop

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 11_0_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36

Browser: Chrome 87

Operating system: Mac OS X 11.0.1

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
Object.assign()	2632.1 Ops/sec
Spread	1787.8 Ops/sec
For-in (no hasOwnProperty check)	2443.2 Ops/sec
For-in (direct hasOwnProperty check)	1951.5 Ops/sec
For-in (indirect hasOwnProperty check)	1679.7 Ops/sec

Script Preparation code:

var orig = {
    hey: "howdy"
}
for (i = 0; i < 1000; i++) {
    orig[Math.random() + ""] = i % 3 === 0 ? "some string blah blah blah" : i % 3 === 1 ? ["a", "b", "c"] : {
        yo: "hello"
    };
}
var hasOwnProperty = Object.prototype.hasOwnProperty;

Tests:

Object.assign()
const clone = Object.assign({}, orig, { hey: "sup" }) clone.hey
Spread
const clone = { ...orig, hey: "sup" } clone.hey
For-in (no hasOwnProperty check)
const clone = {}; for (const k in orig) { clone[k] = orig[k] } clone.hey = "sup" clone.hey
For-in (direct hasOwnProperty check)
const clone = {}; for (const k in orig) { if (orig.hasOwnProperty(k)) { clone[k] = orig[k] } } clone.hey = "sup" clone.hey
For-in (indirect hasOwnProperty check)
const clone = {}; for (const k in orig) { if (hasOwnProperty.call(orig, k)) { clone[k] = orig[k] } } clone.hey = "sup" clone.hey

Run results for: Shallow cloning an object: Object.assign() vs. Spread vs. for-in loop

Object.assign()

Spread

For-in (no hasOwnProperty check)

For-in (direct hasOwnProperty check)

For-in (indirect hasOwnProperty check)