Let's dive into the benchmark being measured on MeasureThat.net.

What is being tested?

The benchmark is comparing two approaches to access the computed style of an element:

1. elem.ownerDocument.defaultView.getComputedStyle(elem)
2. window.getComputedStyle(elem)

These two approaches are testing how efficient and accurate each method is in retrieving the computed style of an element, which includes properties like width, height, color, etc.

Options compared:

There are two options being compared:

A) Using the ownerDocument.defaultView object to access the global CSSOM (CSS Object Model) API. B) Using the window.getComputedStyle() method directly on the window object.

Pros and Cons of each approach:

1. Using elem.ownerDocument.defaultView.getComputedStyle(elem)
   • Pros:
     • More direct and native access to the CSSOM API, which can be more efficient.
     • Can provide better accuracy in terms of handling complex style inheritance scenarios.
   • Cons:
     • Requires accessing the ownerDocument property on the element, which may introduce additional overhead or dependencies.
2. Using window.getComputedStyle(elem)
   • Pros:
     • More straightforward and widely supported method, as it doesn't require access to the ownerDocument property.
     • May be easier to implement and maintain for developers who are not familiar with the CSSOM API.
   • Cons:
     • Can be less efficient due to additional overhead or dependencies introduced by accessing the window object.

Library/Tool usage:

There is no specific library being used in this benchmark, but it relies on the JavaScript Engine and Browser implementations of the getComputedStyle() method. The ownerDocument property is a part of the DOM (Document Object Model) API, which is implemented natively by most browsers.

Special JS feature or syntax:

There are no special JS features or syntax being used in this benchmark beyond standard ECMAScript 2020 language features.

Other alternatives:

Some alternative approaches to accessing the computed style of an element include:

• Using the getComputedStyle() method on a separate CSSStyleRule object, if available.
• Implementing a custom solution using DOM manipulation and CSS selectors.
• Utilizing browser-specific APIs or extensions (e.g., React Query or other optimization libraries).

Keep in mind that these alternatives may have different performance implications, trade-offs, or requirements depending on the specific use case.