Benchmark: Test private variables vs weakmap

Script Preparation code:

window.A = class A {
  get a() { return this._a; }
  set a(v) { this._a = v; }
};

const _wm = new WeakMap();
function _(t) {
  let tt = _wm.get(t);
  if(tt === undefined)
    _wm.set(t, tt = {});
  return tt;
}

window.B = class B {
  get a() { return _(this).a; }
  set a(v) { _(this).a = v; }
};

Tests:

Private variables
const a = new A(); console.log(a.a); a.a = "toto"; console.log(a.a); a.a = "toto2";
Weakmap
const a = new B(); console.log(a.a); a.a = "toto"; console.log(a.a); a.a = "toto2";

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Private variables
Weakmap

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.75 Safari/537.36

Browser/OS: Chrome 73 on Linux

View result in a separate tab

Test name	Executions per second
Private variables	73053.6 Ops/sec
Weakmap	63732.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the Benchmark Definition and individual test cases.

**Benchmark Definition**

The benchmark measures the performance difference between using private variables (`A`) and WeakMap (`B`) in JavaScript.

**Private Variables (A)**

In this approach, private variables are implemented using a class with getter and setter methods. The `get` method returns the value of `_a`, which is not directly accessible from outside the class. This implementation ensures that the variable's value cannot be changed directly from outside the class.

Pros:

* Provides a way to implement private variables, which can help encapsulate data and prevent direct access.
* Can be useful for implementing singletons or other design patterns.

Cons:

* May incur overhead due to the need for getter and setter methods, which can lead to slower performance compared to direct access.
* Can make code harder to read and maintain if not used carefully.

**WeakMap**

In this approach, a WeakMap is used to store values. A WeakMap is a data structure that stores key-value pairs, but does not prevent the garbage collector from freeing the memory allocated to the value when it is no longer referenced elsewhere in the program. This makes it suitable for storing temporary or transient data.

Pros:

* Provides fast and efficient access to data, as it uses a hash table implementation.
* Does not incur overhead due to getter and setter methods.

Cons:

* May not be suitable for use cases where data needs to be protected from direct modification.
* Can lead to memory leaks if not used carefully (e.g., when the key is no longer referenced elsewhere in the program).

**Library**

The WeakMap library is a built-in JavaScript feature. It was introduced in ECMAScript 2014 and provides an efficient way to store small amounts of data.

Pros:

* Fast and efficient access to data.
* Does not incur overhead due to getter and setter methods.

Cons:

* Limited scope, as it can only be used within the current execution context.
* May not be suitable for use cases where data needs to be protected from direct modification or accessed across multiple contexts.

**Special JS Feature/Syntax**

None of the test cases use any special JavaScript features or syntax beyond what is described in the Benchmark Definition.

**Alternatives**

If you need a more robust and feature-rich way to implement private variables, consider using a library like **PrivateClass**, which provides a simple way to create classes with private properties. Alternatively, you can use **Object.freeze()** to make an object's properties immutable, but this approach has its own set of trade-offs.

If you need a more efficient data structure than WeakMap for storing temporary or transient data, consider using **Map** or another hash table implementation.

I hope this explanation helps! Let me know if you have any further questions.

Related benchmarks:

Test private variables vs weakmap (version: 0)

Comparing performance of: Private variables vs Weakmap

Created: 6 years ago by: Guest

Jump to the latest result

Private variables

Weakmap

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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