This benchmark compares the performance of two different methods for checking the presence of values in HTML elements: classList.contains and hasAttribute. The tests are performed on a variety of HTML elements that have both class attributes and other data attributes.

Methods Being Compared:

1. hasAttribute(name) Method:

   • Purpose: Determines whether the specified element has an attribute with the given name. It returns a boolean value indicating the presence (true) or absence (false) of the attribute.
   • Usage in Benchmark: Various elements are tested for the presence of the id attribute, and in some cases, other attributes (class, a, b, etc.).
   • Pros:
     • Directly retrieves whether an attribute exists, which can be useful for elements that may have non-class attributes.
     • Clear semantics when checking for specific attributes.
   • Cons:
     • Generally requires more overhead than checking classes, especially for elements that have many attributes.
     • The performance can vary depending on the number of attributes present.

2. classList.contains(className) Method:

   • Purpose: Checks if the specified class exists in the element's list of classes. It returns a boolean indicating whether the class is present.
   • Usage in Benchmark: Elements are tested for the presence of specific classes (e.g., bar, baz, a, b, etc.).
   • Pros:
     • Designed specifically for class checks, making it potentially faster and more efficient in contexts where you need to verify CSS classes.
     • Provides clearer intent when manipulating CSS classes on elements.
   • Cons:
     • Only works with classes, limiting its utility for attributes outside the realm of CSS.
     • May not be applicable to all use cases, especially for attributes other than class.

Considerations

• Performance:

  • The benchmark results show varying execution speeds for both methods across different test cases. It is notable that checking for the presence of an id attribute generally performed better than checking for some classes.
  • For example, the fastest result recorded was for the hasAttribute method, indicating that it may be more efficient under certain conditions (e.g., simpler elements).

• DOM Structure:

  • The performance of either method can also be impacted by the structure and complexity of the DOM. Elements with more attributes can lead to increased overhead for hasAttribute.

• Element Count:

  • The benchmark included tests with elements that have different counts of classes and attributes. The overhead of DOM manipulation (like creating those elements) also impacts the measurement and should be accounted for when interpreting results.

Alternatives

1. Using jQuery or Other Libraries:

   • Libraries such as jQuery provide utility functions (like .hasClass()) specifically designed for class manipulations. They offer more extensive cross-browser compatibility and additional features but may add overhead compared to native methods.
   • Their internal optimizations might lead to different performance characteristics depending on the use case.

2. Custom Logic:

   • Developers can implement custom functions for checking class presence or attribute existence. However, creating efficient, robust implementations can require significant effort and may not outperform built-in methods.

3. Using CSS Selectors via querySelector:

   • You can check for class presence using document.querySelector with a selector string. While clear and powerful, this may be slower for specific checks compared to the direct classList method.

Conclusion

This benchmark provides insights into the relative performance of two commonly used JavaScript methods for checking class and attribute presence in the context of the DOM. The results highlight circumstances where one might be preferable to the other. Generally, classList.contains is better when working directly with classes, while hasAttribute is suited for broader checks across various attributes, with performance and use cases guiding the choice of one over the other.