Benchmark: WeakMap vs arrays read performance (fixed)

Script Preparation code:

var keys = [];
var values = [];
var weakmap = new WeakMap();
for (let i = 0; i < 100000; i++) {
    const keyobj = {
        key: i
    };
    const valobj = {
        val: `val_${i}`
    };
    keys[i] = keyobj;
    values[i] = valobj;
    weakmap.set(keyobj, valobj);
}

Tests:

arrays
for (let i = 0; i < 100000; i++) { const key = keys[i]; const val = values[key.key]; }
weakmap
for (let i = 0; i < 100000; i++) { const key = keys[i]; const val = weakmap.get(key); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
arrays
weakmap

Fastest: N/A

Slowest: N/A

Latest 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 benchmark and explain what's being tested.

**What is being tested?**

The benchmark tests two approaches to read performance: arrays and WeakMap. Both approaches store key-value pairs, but they differ in how they manage these pairs.

In the `arrays` test case:

*   An array of objects (`keys`) is created, where each object has a unique `key` property.
*   A corresponding array of objects (`values`) is created, where each object has a unique `val` property.
*   The benchmark iterates over the `keys` array and attempts to access the corresponding value in the `values` array using the `key` property.

In contrast, the `weakmap` test case uses a WeakMap data structure:

*   A WeakMap is created, which stores key-value pairs where each key is an object.
*   The benchmark iterates over the same range of numbers and sets the corresponding value in the WeakMap using the `keyobj` as the key.

**Options compared**

The two approaches are being compared to determine which one performs better in terms of read performance.

**Pros and Cons:**

*   **Arrays**:
    *   Pros:
        *   Arrays are a built-in JavaScript data structure, so they're likely to be highly optimized.
        *   Accessing an element in an array using its index is typically very fast (O(1)).
    *   Cons:
        *   This approach can lead to slower performance when dealing with large datasets because arrays require more memory allocation and deallocation than WeakMaps.
*   **WeakMap**:
    *   Pros:
        *   WeakMaps are designed specifically for storing key-value pairs, which makes them optimized for this use case.
        *   They're less memory-intensive than arrays because they don't require additional array indexing overhead.
    *   Cons:
        *   Accessing an element in a WeakMap using its key is slightly slower (O(1) with modern browsers).

**Library and syntax**

There's no specific library being used in this benchmark. The WeakMap data structure is part of the JavaScript standard library.

**Special JS feature or syntax**

None mentioned.

Now, let's take a look at some alternative approaches to comparing these two methods:

*   **Hash tables**: In some cases, using a hash table (e.g., Object.create(null)) could be an alternative to arrays. However, this approach would require additional setup and might not offer significant performance benefits.
*   **Typed Arrays**: Using typed arrays like Int32Array or Float64Array can provide better performance for numerical data. However, this approach wouldn't make sense for storing string values like in the `weakmap` test case.

Overall, the choice between using arrays and WeakMap depends on your specific use case and requirements. If you need to store a large number of key-value pairs and prioritize memory efficiency, WeakMap might be the better option. However, if you're dealing with numerical data or require fast random access to elements, arrays could be a better fit.

Keep in mind that these results are specific to Firefox 100 on Windows. Browsers and environments can vary significantly, so it's essential to consider multiple factors when choosing between different approaches.

Related benchmarks:

WeakMap vs arrays read performance (fixed) (version: 0)

Comparing performance of: arrays vs weakmap

Created: 4 years ago by: Guest

Jump to the latest result

arrays

weakmap

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):