Let's break down the benchmark and explain what's being tested.

Benchmark Overview

MeasureThat.net is testing two different approaches to check if an element has a style attribute set to "none". The test cases are:

1. getComputedStyle: Uses the window.getComputedStyle method to get the computed style of an element.
2. className2: Uses a custom approach by checking the className property of the element.

Test Case 1: getComputedStyle

In this test case, the script preparation code is:

var i = 3000;
var div = document.getElementsByClassName('foo')[0];
while (i--) {
    chekele(div);
}

The chekele function checks if the element's display style is not "none" using window.getComputedStyle(element, null).display.indexOf('none') === -1.

Pros and Cons

• Pros: This approach is simple and straightforward. It directly checks the computed style of the element.
• Cons: This approach can be slower because it involves calling a method that makes an additional HTTP request to retrieve the CSS styles from the server.

Test Case 2: className2

In this test case, the script preparation code is:

var i = 3000;
while (i--) {
    chekele('foo');
}

function chekele(element) {
    return document.getElementsByClassName(element)[0].className.indexOf('hide') === -1;
}

This approach uses a custom function chekele to check if the element's class name includes "hide". This is done by getting the first child element with the given class name using document.getElementsByClassName(element).

Pros and Cons

• Pros: This approach can be faster because it doesn't involve making an additional HTTP request to retrieve CSS styles.
• Cons: This approach relies on the fact that the class names are already present in the HTML code, which might not always be the case.

Library and Special JS Feature

In both test cases, a library (not explicitly mentioned) is used to get elements from the DOM. The document.getElementsByClassName method is used to retrieve elements with a specific class name.

There's no special JavaScript feature or syntax being tested in this benchmark.

Other Alternatives

If you want to measure performance of getting CSS styles using other approaches, you could consider:

1. Using getComputedStyle with a different element (e.g., the root element) to avoid any overhead.
2. Comparing the execution time of window.getComputedStyle with the execution time of className2 in reverse order (i.e., checking if an element is not "hide" instead of checking if it's "none").
3. Using other methods to check if an element has a specific style, such as using CSS APIs like CSSStyle or Web APIs.
4. Adding more complex cases to the benchmark, such as checking multiple styles or using different class names.

Keep in mind that these alternatives might require additional modifications to the script preparation code and the test cases.