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/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36

Browser: Chrome 83

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	3449939.0 Ops/sec
Object.assign with blank object	3049106.0 Ops/sec
Iteration with created object	1331576.0 Ops/sec
Object.assign with created object	1121890.0 Ops/sec
Iteration with blank object and prototype	1078625.0 Ops/sec
Object.assign with blank object and prototype	715272.4 Ops/sec
Iteration with blank object and prototype prop	1564491.0 Ops/sec
Object.assign with blank object and prototype prop	1840001.0 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