Overview

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks, comparing different approaches to test various aspects of the language. In this explanation, we will break down the provided benchmark definition and individual test cases, discussing what each option tests, their pros and cons, and other considerations.

Benchmark Definition

The benchmark definition is a JSON object that describes the benchmark being run:

{
    "Name": "$.hasClass vs RegExp vs indexOf vs classList 2",
    "Description": null,
    "Script Preparation Code": ...,
    "Html Preparation Code": ...
}

This benchmark tests four different approaches to check if an element has a specific class:

1. $ .hasClass (jQuery method)
2. RegExp (regular expression)
3. indexOf (string indexing)
4. classList (DOM API)

Individual Test Cases

Each test case is defined in the "Benchmark Definition" JSON object:

[
    {
        "Benchmark Definition": "...",
        "Test Name": "$.hasClass"
    },
    ...
]

Here's a brief explanation of each test case:

1. $ .hasClass (jQuery method)
   • This test case uses jQuery to check if an element has the specified class.
2. RegExp (regular expression)
   • This test case uses a regular expression to match the class name in the element's className property.
3. Dry RegExp
   • This test case is similar to the previous one but creates a new regular expression object instead of compiling it.
4. indexOf
   • This test case uses string indexing to find the index of the class name in the element's className property.
5. classList
   • This test case uses the DOM API to check if the element has the specified class.
6. hasClassString
   • This test case is similar to $ .hasClass, but it's defined in a separate function.
7. indexOf more than operator
   • This test case is similar to indexOf but uses the "more than" operator ( > -1 ) instead of checking for equality.

Options Compared

The four main options being compared are:

1. $ .hasClass vs RegExp
   • jQuery's hasClass method is generally faster and more efficient than using regular expressions.
2. indexOf vs classList
   • The DOM API's classList.contains() method is faster and more accurate than using string indexing (indexOf).
3. Regular expression vs Dry RegExp
   • Creating a new regular expression object ( Dry RegExp ) does not provide any significant performance benefits over compiling it.

Pros and Cons

Here are some pros and cons for each option:

1. $ .hasClass
   • Pros: Fast, efficient, and widely supported.
   • Cons: Dependent on jQuery library.
2. RegExp
   • Pros: Flexible and powerful, but can be slower due to overhead.
   • Cons: Regular expressions can be complex and error-prone.
3. indexOf
   • Pros: Simple and lightweight, but may not be accurate in some cases.
   • Cons: Can be slower than other options.
4. classList
   • Pros: Fast, efficient, and accurate, with good browser support.
   • Cons: Requires modern browsers.

Other Considerations

1. Browser Support: The benchmark only includes results for Chrome 84 on Windows. Other browsers may have different performance characteristics.
2. Library Dependency: Some tests (e.g., $ .hasClass and classList) rely on external libraries (jQuery or DOM API), which can impact performance.
3. Regular Expressions: While regular expressions are powerful, they can be complex and error-prone, especially for beginners.

In conclusion, this benchmark highlights the importance of considering performance, accuracy, and browser support when choosing an approach to test class presence in JavaScript elements.