Run results for: Object.assign vs iteration performance (Grammarly Focal)

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1 Safari/605.1.15

Browser: Safari 13

Operating system: Mac OS X 10.15.4

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
Iteration with blank object	2191891.0 Ops/sec
Object.assign with blank object	2999995.0 Ops/sec
Iteration with created object	745673.0 Ops/sec
Object.assign with created object	1244523.0 Ops/sec
Iteration with blank object and prototype	595561.7 Ops/sec
Object.assign with blank object and prototype	704486.6 Ops/sec
Iteration with blank object and prototype prop	818192.3 Ops/sec
Object.assign with blank object and prototype prop	850509.3 Ops/sec

Script Preparation code:

class Rectangle {
    constructor(height, width) {
        this.height = height;
        this.width = width;
    }

    calcArea() {
        return this.height * this.width;
    }
}

var r = new Rectangle(3, 4);

Tests:

Iteration with blank object
var copy = {}; for(const prop in r) copy[prop] = r[prop];
Object.assign with blank object
var copy = {}; Object.assign(copy, r);
Iteration with created object
var copy = Object.create(Object.getPrototypeOf(r)); for(const prop in r) copy[prop] = r[prop];
Object.assign with created object
var copy = Object.create(Object.getPrototypeOf(r)); Object.assign(copy, r);
Iteration with blank object and prototype
var copy = {}; Object.setPrototypeOf(copy, Object.getPrototypeOf(r)); for(const prop in r) copy[prop] = r[prop];
Object.assign with blank object and prototype
var copy = {}; Object.setPrototypeOf(copy, Object.getPrototypeOf(r)); Object.assign(copy, r);
Iteration with blank object and prototype prop
var copy = {}; copy.__proto__ = r.__proto__; for(const prop in r) copy[prop] = r[prop];
Object.assign with blank object and prototype prop
var copy = {}; copy.__proto__ = r.__proto__; Object.assign(copy, r);

Run results for: Object.assign vs iteration performance (Grammarly Focal)

Iteration with blank object

Object.assign with blank object

Iteration with created object

Object.assign with created object

Iteration with blank object and prototype

Object.assign with blank object and prototype

Iteration with blank object and prototype prop

Object.assign with blank object and prototype prop