Benchmark: className + attribute vs attribute + className

HTML Preparation code:

<div class="testClass" data-name="testDataset"></div>

Tests:

className + attribute
var nodeEl = document.querySelector('.testClass[data-name="testDataset"]');
attribute + className
var nodeEl = document.querySelector('[data-name="testDataset"].testClass');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
className + attribute
attribute + className

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

**What is being tested?**

On MeasureThat.net, the provided benchmark tests two different ways of selecting an HTML element using JavaScript. The test compares how fast these two approaches are.

The first approach uses a CSS selector with class and attribute together: `.testClass[data-name="testDataset"]`. The second approach uses a CSS selector where the attribute is specified first and then the class: `[data-name="testDataset"].testClass`.

**Options being compared**

There are only two options being compared:

1. **`className + attribute`**: This approach uses the class name followed by the attribute to select an element.
2. **`attribute + className`**: This approach uses the attribute followed by the class name to select an element.

**Pros and Cons of each approach:**

* **`className + attribute`**
	+ Pros:
		- Can be more readable, as it clearly indicates the order in which elements are being selected.
		- Might be faster, since the browser can use a single step to access the DOM (i.e., by CSS class name), and then apply the attribute filter later.
	+ Cons:
		- Can lead to slower performance if there are many elements with the same class but different attributes, as the browser has to iterate over the attribute values to find a match.
* **`attribute + className`**
	+ Pros:
		- Can be faster in some cases (e.g., when there are many elements with the same attribute value), since the browser can use a single step to access the DOM and then apply the class name filter later.
	+ Cons:
		- Can lead to slower performance if there are many elements with the same class but different attributes, as the browser has to iterate over the class names to find a match.

**Library used**

In this benchmark, no specific JavaScript library is required. The HTML element selection is done using native JavaScript (i.e., `document.querySelector()`).

**Special JS features or syntax**

There are no special JavaScript features or syntax used in this benchmark. It only relies on standard JavaScript APIs and CSS selectors.

**Other alternatives**

If you're looking for alternative ways to select elements, there are other approaches:

* **`element.children[0]`**: This approach can be faster if you need to select the first child element of a container element.
* **`Array.from(element.querySelectorAll(selector))`**: This approach can be more flexible if you need to apply multiple filters or transformations to the selected elements.

However, these alternatives are not being tested in this specific benchmark.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.88 Safari/537.36

Browser/OS: Chrome 100 on Windows

View result in a separate tab

Test name	Executions per second
className + attribute	4024005.8 Ops/sec
attribute + className	4010204.2 Ops/sec

Related benchmarks:

className + attribute vs attribute + className (version: 0)

Comparing performance of: className + attribute vs attribute + className

Created: 2 years ago by: Guest

Jump to the latest result

className + attribute

attribute + className

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):