Benchmark: getElementsByClassName/querySelectorAll

HTML Preparation code:

<div class="main">
  <div class="outer1">
	<div class="inner">
      text
    </div>
  </div>
  <div class="outer2">
	<div class="inner">
      text
    </div>
  </div>
</div>

Tests:

getElementsByClassName
document.getElementsByClassName("inner")
querySelectorAll
document.querySelectorAll(".inner")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementsByClassName
querySelectorAll

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its test cases.

**What is being tested?**

The benchmark measures the performance of two different methods to retrieve elements from an HTML document:

1. `getElementsByClassName`
2. `querySelectorAll`

These methods are used to select elements based on their class names or selectors, respectively.

**Options compared**

The benchmark compares the execution speed of these two methods across different browsers (in this case, only Firefox 107) and devices (Desktop).

**Pros and Cons of each approach:**

1. `getElementsByClassName`:
	* Pros:
		+ Widely supported in older browsers
		+ Can be used to retrieve elements based on a specific class name
	* Cons:
		+ Not as efficient as `querySelectorAll`
		+ May return more elements than needed, leading to slower performance
2. `querySelectorAll`:
	* Pros:
		+ More efficient and modern approach
		+ Can be used with a wider range of selectors (e.g., IDs, class names, attributes)
	* Cons:
		+ Less supported in older browsers
		+ May not work as expected if the selector is incorrect or not present

**Library and its purpose**

In both test cases, the `document` object is used, which is a global object in JavaScript that provides access to various DOM (Document Object Model) elements.

**Special JS feature/syntax**

None mentioned in this benchmark. However, it's worth noting that `querySelectorAll` uses a CSS selector syntax, which can be complex and prone to errors if not used correctly.

**Other alternatives**

There are other methods to retrieve elements from an HTML document, such as:

* `getElementsByTagName()`: Retrieves elements based on their tag name.
* `getElementById()`: Retrieves an element by its ID attribute.
* `querySelector` (without the `all` method): Similar to `querySelectorAll`, but only returns the first match.

However, these alternatives are not being tested in this benchmark. The focus is specifically on comparing the performance of `getElementsByClassName` and `querySelectorAll`.

**Benchmark preparation code**

The provided HTML structure uses class names (`main`, `outer1`, `outer2`, `inner`) to identify elements. This allows for a simple and consistent way to test the performance of these methods.

I hope this explanation helps you understand what's being tested in this benchmark!

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:107.0) Gecko/20100101 Firefox/107.0

Browser/OS: Firefox 107 on Windows

View result in a separate tab

Test name	Executions per second
getElementsByClassName	5044888.5 Ops/sec
querySelectorAll	1099700.2 Ops/sec

Related benchmarks:

getElementsByClassName/querySelectorAll (version: 0)

Comparing performance of: getElementsByClassName vs querySelectorAll

Created: 3 years ago by: Guest

Jump to the latest result

getElementsByClassName

querySelectorAll

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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