Run results for: private properties in weakmap vs symbol vs # class syntax

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/116.0

Browser: Firefox 116

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
WeakMap	5088265.5 Ops/sec
Class	6550710.5 Ops/sec

Script Preparation code:

class Person {
	static #counter = 0
	#age
	constructor(name, age) {
		this.name = name;
		this.#age = age;
	}
	showPublic() {
		return this.name;
	}
	showPrivate() {
		return this.#age;
	}
}

window.__person = new Person("j", 22)


// WeakMap
const privKs = new WeakMap();

const proto = {
	showPrivate() {
		return privKs.get(this).age
	},
	showPublic() {
		return this.name
	}
}
function User(name, age) {
	const obj = {name, age}
	privKs.set(obj, {age})
	return Object.setPrototypeOf(obj, proto)
}

window.__user = User("j", 11)


// Symbols
const priv_ = Symbol("private data")

const proto2 = {
	showPrivate() {
		return this[priv_].age
	},
	showPublic() {
		return this.name
	}
}

function Teacher(name, age) {
	const obj = {name, [priv_]: {age}}
	return Object.setPrototypeOf(obj, proto2)
}

window.__teacher = Teacher("j", 22)

Tests:

Class
window.__person.showPrivate()
WeakMap
window.__user.showPrivate()
Symbols
window.__teacher.showPrivate()

Run results for: private properties in weakmap vs symbol vs # class syntax

Class

WeakMap

Symbols