Benchmark: private properties in weakmap vs symbol vs # class syntax

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()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Class
WeakMap
Symbols

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:139.0) Gecko/20100101 Firefox/139.0

Browser/OS: Firefox 139 on Windows

View result in a separate tab

Symbols

5.3M/s

Class

5.2M/s

WeakMap

4.6M/s

View exact numbers

Test name	Executions per second
✓ Symbols	5,303,464 Ops/sec
Class	5,153,154 Ops/sec
WeakMap	4,626,446 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and explain what is being tested, compared, and their pros and cons.

**Benchmark Definition:**

The benchmark measures the performance of three different approaches to store private data in JavaScript:

1. **Class syntax**: Using a class with a private property (`#age`) and getter methods for public and private access.
2. **WeakMap**: Using a WeakMap to store an object with private data, where the key is another object that contains the private data.
3. **Symbols**: Using a symbol as a private property key, similar to a WeakMap.

**Options Compared:**

* Class syntax (using `#` notation for private properties)
* WeakMap
* Symbols

**Pros and Cons of Each Approach:**

1. **Class syntax**:
	* Pros:
		+ Easy to understand and implement
		+ Provides strong typing and type checking at runtime
	* Cons:
		+ May lead to over-engineering or unnecessary complexity
		+ Can be slower due to the overhead of getter methods
2. **WeakMap**:
	* Pros:
		+ Fast and lightweight
		+ Flexible, as it allows for custom key objects
	* Cons:
		+ May require more manual memory management (e.g., garbage collection)
		+ Can be less intuitive to use, especially for those without prior experience with WeakMaps
3. **Symbols**:
	* Pros:
		+ Fast and lightweight
		+ Similar syntax to object property access (i.e., `obj[priv_]`)
	* Cons:
		+ May lead to naming conflicts if not used carefully
		+ Can be less readable or maintainable, especially in complex codebases

**Library Usage:**

The benchmark uses the following libraries:

1. **`WeakMap`**: A built-in JavaScript object that stores mappings of values to keys using weak references.
2. **`Symbol`**: A built-in JavaScript primitive used to create unique symbols.

**Special JS Feature/Syntax:**

None mentioned in this explanation.

**Other Alternatives:**

If you need alternative approaches, consider the following:

1. **Object.freeze() and getter methods**: Use `Object.freeze()` to create an immutable object with private properties, accessed via getter methods.
2. **Proxy objects**: Create proxy objects using the `Proxy` constructor to control access to private data.
3. **Encapsulate with a closure**: Encapsulate data within a closure to limit its scope and accessibility.

Keep in mind that these alternatives may have trade-offs in terms of performance, readability, or maintainability, depending on your specific use case.

**Benchmark Preparation Code Explanation:**

The provided script creates three classes (`Person`, `User`, and `Teacher`) with different approaches to store private data:

* Class syntax: uses the `#` notation for private properties
* WeakMap: stores an object with private data using a WeakMap
* Symbols: uses a symbol as a private property key

Each class has getter methods for public and private access.

The script also defines a `proto` and `proto2` objects, which serve as the prototype for each class. The `User` and `Teacher` constructors use these prototypes to create new instances with the specified private data.

In summary, this benchmark compares three approaches to store private data in JavaScript: Class syntax using getter methods, WeakMap, and Symbols.

private properties in weakmap vs symbol vs # class syntax (version: 3) Benchmark.js

Comparing performance of: `Class vs WeakMap vs Symbols`

Created: 3 years ago by: Registered User

Go to the latest result

Class

WeakMap

Symbols

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

private properties in weakmap vs symbol vs # class syntax (version: 3) Benchmark.js

Comparing performance of: Class vs WeakMap vs Symbols

Created: 3 years ago by: Registered User

Go to the latest result

Class

WeakMap

Symbols

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Related benchmarks

Comparing performance of: `Class vs WeakMap vs Symbols`