Benchmark: querySelectorAll vs getElementsByClassName claudiu

Tests:

querySelectorAll
document.querySelectorAll('.test')
getElementsByClassName
document.getElementsByClassName('.test')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelectorAll
getElementsByClassName

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the provided benchmark.

**What is being tested?**

The benchmark measures the performance difference between two methods for selecting HTML elements: `document.querySelectorAll()` and `document.getElementsByClassName()`. The test case uses an HTML string with a div element that has both a `name` attribute, an `id` attribute, and a `class` attribute containing the value `'test'`.

**Options being compared**

The two options being compared are:

1. **`document.querySelectorAll('.test')`**: This method returns a NodeList of all elements that have the specified class.
2. **`document.getElementsByClassName('test')`**: This method returns an HTMLCollection of all elements that have the specified class.

**Pros and Cons:**

*   `document.querySelectorAll('.test')`:
    *   Pros:
        *   More flexible, as it allows for using multiple classes or a CSS selector.
        *   Returns a NodeList, which can be iterated over more easily than an HTMLCollection.
    *   Cons:
        *   May have higher overhead due to the use of a CSS selector.
*   `document.getElementsByClassName('test')`:
    *   Pros:
        *   Faster, as it uses a direct reference to the element's class attribute.
    *   Cons:
        *   Less flexible than `querySelectorAll()`, as it can only select elements with the exact class value.
    *   The result is an HTMLCollection, which may not be as convenient to work with as a NodeList.

**Library and its purpose**

The benchmark does not use any external libraries. However, both methods rely on the browser's DOM implementation for their functionality.

**Special JS feature or syntax**

There are no special JavaScript features or syntax used in this benchmark. Both methods are standard DOM API methods that have been part of JavaScript since the early days of web development.

**Other alternatives:**

For selecting elements based on classes, you could also use:

1.  **`document.querySelector()`**: This method returns a single element that matches the specified CSS selector. If no elements match, it returns null.
2.  **`document.querySelectorAll(selector)`**: Similar to `querySelectorAll()`, but allows for using a more complex CSS selector.

However, since this benchmark is specifically comparing the performance of `querySelectorAll()` and `getElementsByClassName()`, using other methods like `querySelector()` would not be relevant.

These alternatives can be used in different scenarios where you need to select elements based on classes or CSS selectors. However, for simple cases, `document.querySelectorAll()` or `document.getElementsByClassName()` might still be the best choice due to their simplicity and performance characteristics.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/111.0

Browser/OS: Firefox 111 on Windows

View result in a separate tab

Test name	Executions per second
querySelectorAll	1883632.8 Ops/sec
getElementsByClassName	8493377.0 Ops/sec

Related benchmarks:

querySelectorAll vs getElementsByClassName claudiu (version: 0)

<div name='test' id='test' class='test'> <div class='test-child'></div> </div>

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: one year ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByClassName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):