Overview

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. In this case, we're analyzing a benchmark that compares the performance of three methods to select elements with a specific attribute or class name: querySelectorAll, getElementsByClassName, and accessing an element's data-attribute directly.

What is tested?

The benchmark tests the execution speed of these three approaches in the following test cases:

1. data-attribute: Accessing an element's data-attribute directly.
2. querySelectorAll: Using the querySelectorAll() method to select elements with a specific class name or attribute value.
3. getElementsByClassName: Using the getElementsByClassName() method to select elements with a specific class name.

Options compared

The benchmark compares the performance of three options:

1. Direct access: Accessing an element's data-attribute directly using the dot notation (test.data-attribute).
2. querySelectorAll: Using the querySelectorAll() method to select elements with a specific class name or attribute value.
3. getElementsByClassName: Using the getElementsByClassName() method to select elements with a specific class name.

Pros and Cons

Here are some pros and cons of each approach:

1. Direct access: Pros:
   • Fastest, as it involves only a single property access.
   • Most readable and intuitive. Cons:
   • May not work consistently across different browsers or versions.
2. querySelectorAll:
   • Pros:
     • Works consistently across different browsers and versions.
     • Can be used to select multiple elements at once.
   • Cons:
     • May be slower than direct access due to the additional overhead of parsing the CSS selector.
     • Requires an explicit class name or attribute value, which may not always be present.
3. getElementsByClassName:
   • Pros:
     • Works consistently across different browsers and versions.
     • Can be used to select multiple elements at once.
   • Cons:
     • May be slower than direct access due to the additional overhead of parsing the class name or attribute value.
     • Returns an array of elements, which may require additional processing.

Library usage

None of the test cases use any external libraries. The querySelectorAll and getElementsByClassName methods are built-in to the DOM API.

Special JS features or syntax

There are no special JavaScript features or syntax used in this benchmark. It only uses standard ECMAScript syntax for accessing elements by attribute or class name.

Other alternatives

If you need to select elements with a specific attribute value, you may also use the getAttribute() method, which is another built-in DOM API method. However, this method returns a string value, whereas querySelectorAll and getElementsByClassName return an array of elements.