Benchmark: My querySelectorAll vs getElementsByClassName

HTML Preparation code:

<div class="test"></div>
<div class="test"></div>
<div class="test"></div>

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

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:85.0) Gecko/20100101 Firefox/85.0

Browser/OS: Firefox 85 on Windows

View result in a separate tab

Test name	Executions per second
querySelectorAll	621662.6 Ops/sec
getElementsByClassName	2647323.8 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 world of JavaScript microbenchmarks on MeasureThat.net.

**What is being tested?**

The provided benchmark tests two ways to select elements in HTML: `querySelectorAll` and `getElementsByClassName`. Both methods are used to retrieve a list of elements that match a specific CSS selector or class name.

**Options compared**

In this benchmark, we have two options:

1. **`querySelectorAll`**: This method returns a NodeList (an array-like object) containing all elements that match the specified CSS selector. The `querySelectorAll` method is generally more efficient than `getElementsByClassName`, as it doesn't require parsing the class names.
2. **`getElementsByClassName`**: This method returns an HTMLCollection (a collection of DOM nodes) containing all elements with a class name matching the specified string.

**Pros and Cons**

* **`querySelectorAll`**:
	+ Pros: More efficient, as it doesn't require parsing class names.
	+ Cons: Can be slower for very large selections, as it needs to create an array-like object. Also, some browsers might not support it well, like Internet Explorer.
* **`getElementsByClassName`**:
	+ Pros: Can be faster for very large selections, as it doesn't need to create an array-like object.
	+ Cons: Requires parsing the class names, which can be slower.

Other considerations:

* In modern browsers, both methods are generally fast enough for most use cases. However, if you're working with a very large dataset or performance-critical code, using `querySelectorAll` might provide better results.
* The choice between these two methods ultimately depends on the specific requirements of your project and the browser support needed.

**Library usage**

In this benchmark, neither library is explicitly used. Both methods are built-in to the DOM API.

**Special JavaScript feature or syntax**

There's no special JavaScript feature or syntax being tested here. This is a simple comparison of two DOM selection methods.

**Other alternatives**

If you're looking for alternative ways to select elements in HTML, consider:

* **`querySelector`**: A more general-purpose method that can be used to select an element based on a CSS selector.
* **`getElementsByTagName`**: A method that returns an HTMLCollection containing all elements with the specified tag name.

These alternatives might provide different performance characteristics depending on your specific use case and browser support.

Related benchmarks:

My querySelectorAll vs getElementsByClassName (version: 0)

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: 3 years 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 2 months ago):