Benchmark: Class vs Generic Class Selector

HTML Preparation code:

<div class="hello-3wLKDe">Hello</div>

Tests:

Class
document.querySelector('.hello-3wLKDe');
Generic Class
document.querySelector('[class^=hello]');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Class
Generic Class

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated one month ago):

LLMs can make mistakes. Check important info.

Let's break down what's being tested on MeasureThat.net.

**Benchmark Definition**

The benchmark is called "Class vs Generic Class Selector". The description suggests that it's testing the performance of two different approaches to selecting an HTML element using CSS selectors in JavaScript.

**Test Cases**

There are two test cases:

1. **"Class"**: This test case uses `document.querySelector('.hello-3wLKDe');` to select an HTML element with a class of "hello-3wLKDe".
2. **"Generic Class"**: This test case uses `document.querySelector('[class^=hello]');` to select any HTML element whose class starts with "hello".

**Latest Benchmark Result**

The results show that:

* The "Class" approach ( selecting an element by its exact class) runs at approximately 4,675,119 executions per second on a Firefox 118 browser.
* The "Generic Class" approach (selecting elements whose class starts with "hello") runs at approximately 4,084,008 executions per second on the same browser.

**What's being compared?**

The two approaches are being compared in terms of their performance (measured by executions per second). Specifically:

* **Exact Class Match**: This approach requires an exact match of the class name ("hello-3wLKDe") to select the target element.
* **Generic Class Match**: This approach selects any element whose class starts with "hello", potentially matching multiple elements.

**Pros and Cons**

Here are some pros and cons of each approach:

### Exact Class Match

Pros:

* Faster performance (as shown in the benchmark results)
* More targeted selection, reducing the risk of selecting unwanted elements

Cons:

* Requires an exact match of the class name
* May not work if the target element has a different class name, even if it starts with "hello"

### Generic Class Match

Pros:

* Can select multiple elements that have a class starting with "hello"
* More flexible than exact class matching

Cons:

* Slower performance (as shown in the benchmark results)
* May select unwanted elements, especially if there are multiple classes on an element

**Library and Special JS Features**

There is no external library mentioned in this benchmark. However, `document.querySelector()` is a built-in method in modern browsers for selecting HTML elements based on various criteria.

**Other Considerations**

When choosing between these two approaches, consider the following factors:

* Performance: If speed is critical, using an exact class match may be preferable.
* Flexibility: If you need to select multiple elements that share a common prefix in their classes, a generic class match might be more suitable.
* Maintainability: Using a generic class match can make your code more maintainable if the target element's class name changes.

**Other Alternatives**

If these approaches don't meet your needs, consider using:

* `document.querySelector('[class~="hello"]')`: Select elements whose class list includes "hello".
* `document.querySelectorAll()` and filtering the results: Select all elements that match a certain criteria (like having a class starting with "hello") and then filter the result set to get the desired elements.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/118.0

Browser/OS: Firefox 118 on Windows

View result in a separate tab

Test name	Executions per second
Class	4675119.5 Ops/sec
Generic Class	4084007.8 Ops/sec

Related benchmarks:

Class vs Generic Class Selector (version: 0)

Stop saying its slow and start writing good custom CSS for discord that doesn't break

Comparing performance of: Class vs Generic Class

Created: one year ago by: Registered User

Jump to the latest result

Class

Generic Class

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated one month ago):