Let's break down what's being tested in this benchmark.

Benchmark Definition

The benchmark is comparing two approaches to check if an element has a specific class: className.indexOf and classList.contains. These methods are used to achieve the same goal, but with different syntax and semantics.

Options Compared

The two options being compared are:

1. className.indexOf: This method searches for the specified value in the className property of an element. If found, it returns the index of the occurrence; otherwise, it returns -1.
2. classList.contains: This method checks if a specific class is present in the classList property of an element.

Pros and Cons

className.indexOf

Pros:

• Shorter syntax
• Can be used to check for multiple classes by chaining calls (e.g., element.className.indexOf('bar') && element.className.indexOf('baz'))
• Works with older browsers that don't support classList

Cons:

• Less efficient than classList.contains because it performs a linear search
• Returns the index of the first occurrence, not just whether the class is present

classList.contains

Pros:

• More efficient than className.indexOf
• Returns only whether the class is present, without unnecessary indexing information
• Works with modern browsers that support classList

Cons:

• Longer syntax
• May not work as expected if the class name contains spaces or special characters (as it simply performs a substring search)

Library Used

In this benchmark, the classList property is being used, which is a part of the DOM Standard (ECMAScript 2015). The classList.contains method is a built-in method that allows checking for class presence in modern browsers.

Special JS Feature or Syntax

This benchmark uses the ES6 classList API, which is a newer feature introduced in ECMAScript 2015. This API provides a more efficient and convenient way to work with classes in JavaScript.

Other Alternatives

If you need to support older browsers that don't support classList, you can use alternative methods such as:

• Using regular expressions (element.className.match(new RegExp('\\bbar\\b')))
• Using the indexOf method on the class names array (element.className.indexOf('bar') === -1)
• Creating a custom function to check for class presence

However, these alternatives may not be as efficient or convenient as using classList.contains.

In summary, this benchmark is testing the performance difference between two approaches to check if an element has a specific class: className.indexOf and classList.contains. The latter is more efficient and modern, but requires longer syntax.