Benchmark: class query vs data query

HTML Preparation code:

<div class="test"></div>
<div data-test="1"></div>

Tests:

Get by data
document.querySelector('[data-test="1"]')
Get by class
document.getElementsByClassName('.test');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Get by data
Get by class

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:85.0) Gecko/20100101 Firefox/85.0

Browser/OS: Firefox 85 on Ubuntu

View result in a separate tab

Test name	Executions per second
Get by data	995540.9 Ops/sec
Get by class	3522497.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark JSON and explain what's being tested, compared, and the pros/cons of each approach.

**Benchmark Definition**

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

1. **Class Query**: `document.querySelector('[data-test="1"]')`
2. **Data Attribute Query**: `document.getElementsByClassName('.test');`

Both methods are used to retrieve elements with specific attributes or properties.

**Approaches and their pros/cons**

### Class Query (`document.querySelector`)

* **Pros**:
	+ Faster, since it only looks at the element's class list.
	+ Can be more efficient for large sets of elements with similar classes.
* **Cons**:
	+ May not work correctly if the element has multiple classes or if the class name is a valid CSS selector (e.g., `.class`).
	+ Requires the exact class name, which may lead to false negatives.

### Data Attribute Query (`document.getElementsByClassName`)

* **Pros**:
	+ More flexible than class query, as it can look at any attribute, not just classes.
	+ Can be more reliable, since it checks for the presence of a specific attribute on all elements, regardless of other attributes or properties.
* **Cons**:
	+ Slower, since it needs to iterate over all elements in the DOM and check each one's data attributes.
	+ May perform poorly if there are many elements with similar data attributes.

**Library usage**

None of the benchmark tests seem to use any external libraries. The `document.querySelector` and `document.getElementsByClassName` methods are built-in JavaScript APIs.

**Special JS features or syntax**

There is no special JS feature or syntax being tested in this benchmark. Both tests only rely on standard JavaScript DOM traversal methods.

**Other alternatives**

For data attribute queries, other approaches could be:

* Using the `getAttribute` method to retrieve the specific attribute value: `document.querySelector('[data-test="1"]').getAttribute('data-test')`
* Using a CSS selector with the `:has` pseudo-class to select elements that have the specified attribute: `document.querySelectorAll('[data-test="1"]:has([data-foo="bar"])')`

These alternatives would likely be slower and less efficient than using `document.getElementsByClassName`.

Overall, this benchmark provides a simple comparison of two common DOM traversal methods in JavaScript. The results can help developers understand which approach is faster and more reliable for their specific use cases.

Related benchmarks:

class query vs data query (version: 0)

Comparing performance of: Get by data vs Get by class

Created: 3 years ago by: Guest

Jump to the latest result

Get by data

Get by class

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):