Benchmark: Test wildcard selectors with and without tag 2

HTML Preparation code:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.1/jquery.min.js">
</script>
<div>
  <ul>
    <li>
      <a href="#" name="name" class="classname">item 1</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 2</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 3</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 4</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 5</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 6</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 7</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 8</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 9</a>
    </li>
    <li id="last">
      <a href="#" name="name" class="classname">item 10</a>
    </li>
  </ul>
</div>

Script Preparation code:

var node;

Tests:

no tag
node = document.querySelectorAll('[class*="classname"]');
with tag
node = document.querySelectorAll('a[class*="classname"]');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
no tag
with tag

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated yesterday):

LLMs can make mistakes. Check important info.

The benchmark on MeasureThat.net evaluates the performance of two different CSS selector queries in JavaScript, specifically using the `document.querySelectorAll` method. This method is part of the DOM (Document Object Model) API and allows developers to select elements from the HTML document using CSS selectors.

### Test Cases

1. **No Tag Selector**: 
   - **Benchmark Definition**: `node = document.querySelectorAll('[class*="classname"]');`
   - **Description**: This test uses a generic selector that matches all elements with a class containing the string "classname" regardless of their tag.
   - **Pros**: More general and flexible as it can match any element, making it useful when the exact tag type is not known or relevant.
   - **Cons**: May lead to lower performance in larger documents, as it has to check all elements for a matching class rather than narrowing it down to a specific tag.

2. **With Tag Selector**: 
   - **Benchmark Definition**: `node = document.querySelectorAll('a[class*="classname"]');`
   - **Description**: This test uses a more specific selector targeting only `<a>` (anchor) elements that have a class containing "classname".
   - **Pros**: More efficient in terms of performance since the selector is more specific, reducing the number of elements to check and potentially lowering the computational overhead.
   - **Cons**: Less flexible, as it only matches anchor elements and would miss out on other elements that may also have the same class but are of different types.

### Performance Results

From the provided results, we see the number of executions per second for each test case:

- **No Tag**: 1,358,613 executions per second
- **With Tag**: 1,319,794.25 executions per second

This indicates that the more general selector (`no tag`) performed better in this specific instance, which may seem counterintuitive as one might expect more specific selectors to be faster. The reasons could vary based on several factors such as the way the browser's rendering engine optimizes DOM queries, the structure of the DOM, or even the state of the JavaScript engine at the time of execution.

### Considerations and Alternatives

- **CSS Selectors**: The benchmark tests CSS attribute selectors (`[class*="classname"]`) and tag selectors (`'a[class*="classname"]'`). 
- **Performance**: It's important to remember that performance can vary significantly based on the structure of the DOM, the number of elements present, and how a particular browser implements these queries. Browser optimizations could make a difference in the actual execution times.
  
### Other Alternatives

While `document.querySelectorAll` is a modern and flexible approach, alternative methods for selecting elements include:

- **`getElementsByClassName`**: This method returns all elements that have a specified class name and can be faster in cases where selecting by class is needed exclusively, but it lacks the specificity of using attribute selectors.
- **`getElementsByTagName`**: Similar to `getElementsByClassName`, but used for selecting by tag name.
- **jQuery or Other Libraries**: If using a library like jQuery, its selectors would wrap the native selector functions, offering additional features and possibly optimized selection methods. However, this comes with the overhead of including the library and can be slower in pure performance compared to native methods since the library introduces abstraction.

### Conclusion

This benchmark provides valuable insights into the performance of different selector strategies in JavaScript. When making decisions on which selector to use, one should consider both the flexibility required and the performance implications, keeping in mind specific use cases and the structure of the DOM involved.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
no tag	1358613.0 Ops/sec
with tag	1319794.2 Ops/sec

Related benchmarks:

Test wildcard selectors with and without tag 2 (version: 1)

Comparing performance of: no tag vs with tag

Created: 2 days ago by: Guest

Jump to the latest result

no tag

with tag

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated yesterday):