Benchmark: WeakMap vs "Symbol with WeakMap fallback" v2

Script Preparation code:

var c = Symbol === undefined
? (function() {
  var x = function() {
    this._x = new WeakMap();
  }
  x.prototype.get = function(x) { return this._x.get(x); };
  x.prototype.set = function(x,y) { this._x.set(x,y); };
  return x;
})()
: (function() {
  var x = function() {
    this._x = Symbol();
  }
  x.prototype.get = function(x) { return x[this._x]; };
  x.prototype.set = function(x,y) { x[this._x] = y; };
  return x;
})();

var to0 = {};
var to1 = {};
var wm = new WeakMap();
var fwm = new c();
wm.set(to1, 1);
fwm.set(to1, 1);

Tests:

WeakMap get
let r = wm.get(to1);
Symbol with WeakMap fallback get
let r = fwm.get(to1);
WeakMap set
wm.set(to0, 1);
Symbol with WeakMap fallback set
fwm.set(to0, 1);
has
let r = wm.has(to1);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
WeakMap get
Symbol with WeakMap fallback get
WeakMap set
Symbol with WeakMap fallback set
has

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON benchmark and explain what's being tested.

**Benchmark Definition**

The benchmark measures the performance of two approaches for implementing weak maps (a data structure that stores key-value pairs, where the key is a weak reference) in JavaScript:

1. **WeakMap**: A built-in JavaScript object that provides a way to store key-value pairs with weak references.
2. **"Symbol with WeakMap fallback" v2**: An alternative implementation that uses a symbol (a unique identifier) as a key and a WeakMap as the underlying storage.

**Options Compared**

The benchmark compares the performance of these two approaches for the following operations:

* `get`: Retrieving a value associated with a given key.
* `set`: Setting a value associated with a given key.
* `has`: Checking if a key exists in the map without retrieving its value.

**Pros and Cons**

**WeakMap:**

Pros:

* Built-in JavaScript object, ensuring good support and performance.
* Easy to use and understand.
* Fast lookup, insertion, and deletion operations.

Cons:

* May have limitations or quirks depending on the browser or engine used.

**"Symbol with WeakMap fallback" v2:**

Pros:

* Custom implementation that can be optimized for specific use cases or browsers.
* Can provide better performance in certain scenarios.
* Allows for fine-grained control over the implementation.

Cons:

* More complex and harder to understand, especially for those without experience with JavaScript internals.
* May not work well with older browsers or engines.

**Library Usage**

In this benchmark, the `WeakMap` object is used directly. There are no external libraries involved.

**Special JS Features or Syntax**

The implementation uses a technique called "symbol polyfill" to support symbol-based keying in older browsers that don't natively support symbols. This allows the fallback approach to work across different browsers and engines.

**Other Alternatives**

If you're looking for alternative approaches, you might consider:

* Using `Object.assign()` or other methods to implement a weak map-like data structure.
* Utilizing libraries like `weakmap` (a polyfill for WeakMap) or `fast-weak-map` (an optimized implementation of WeakMap).
* Investigating other data structures, such as `Map` with a custom wrapper or a third-party library that provides weak map-like functionality.

Keep in mind that these alternatives may have their own trade-offs and performance characteristics.

Related benchmarks:

WeakMap vs "Symbol with WeakMap fallback" v2 (version: 0)

Comparing performance of: WeakMap get vs Symbol with WeakMap fallback get vs WeakMap set vs Symbol with WeakMap fallback set vs has

Created: 3 years ago by: Guest

Jump to the latest result

WeakMap get

Symbol with WeakMap fallback get

WeakMap set

Symbol with WeakMap fallback set

has

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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