Benchmark: querySelectorAll vs getElementsByClassName

HTML Preparation code:

<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

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark is comparing two ways to select HTML elements in JavaScript:

1. `document.querySelectorAll(".test")`
2. `document.getElementsByClassName(".test")`

These two methods are used to retrieve all elements with a specific class name.

**Options Compared**

The benchmark is testing the performance of these two methods on the same HTML element with the class "test".

**Pros and Cons of Each Approach**

1. **`document.querySelectorAll(".test")`**
	* Pros:
		+ More efficient, as it returns an array-like object (`NodeList`) instead of individual elements.
		+ Can be more flexible when dealing with CSS selectors, allowing for use of attribute selectors, pseudo-classes, and more complex selectors.
	* Cons:
		+ May require additional processing to convert the NodeList to a traditional array or manipulate its contents.
2. **`document.getElementsByClassName(".test")`**
	* Pros:
		+ Easier to understand and use for simple class-based selection.
		+ Returns individual elements (as an HTMLCollection), which can be more convenient in some cases.
	* Cons:
		+ Less efficient, as it returns a collection of individual elements rather than a single array-like object.

**Library and Purpose**

In this benchmark, there is no explicitly mentioned library. However, `document.querySelectorAll` and `document.getElementsByClassName` are part of the DOM (Document Object Model), which is an API for interacting with HTML and XML documents in web browsers.

**Special JS Feature or Syntax**

There is no special JavaScript feature or syntax being tested in this benchmark. Both methods use standard CSS selectors to target elements with a specific class name.

**Other Alternatives**

If you need to select elements based on other attributes, classes, IDs, or pseudo-classes, the following alternatives could be considered:

* `document.querySelector(".test")` for selecting a single element (using the same CSS selector syntax).
* `querySelectorAll` with a more complex CSS selector (e.g., `[data- attribute="foo"]`) to select elements based on attributes.
* `getElementsByClassName` or `getElementsByAttribute` with a specific value (e.g., `.test` or `foo=bar`) to select elements based on class names or attribute values.

Keep in mind that these alternatives may have different performance characteristics and trade-offs, depending on the specific use case.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:80.0) Gecko/20100101 Firefox/80.0

Browser/OS: Firefox 80 on Windows

View result in a separate tab

Test name	Executions per second
querySelectorAll	1292809.8 Ops/sec
getElementsByClassName	5380436.0 Ops/sec

Related benchmarks:

querySelectorAll vs getElementsByClassName (version: 0)

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: 6 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 29 days ago):