Benchmark Overview

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The provided benchmark measures the performance of two approaches: creating an HTML structure using document.createElement vs cloning an existing structure from the DOM using cloneNode.

Script Preparation Code

The script preparation code is not provided, but it's likely that it includes a setup function that creates a test environment and sets up any necessary variables.

Html Preparation Code

The HTML preparation code is:

<div class='container'>
  <div>
    <a href=\"#\">link</a>
  </div>
</div>

<div id="appendedItems"></div>

This code creates two nested <div> elements, which will be used as the base structure for creating new HTML elements.

Individual Test Cases

There are two test cases:

1. createElement
   • This test case uses document.createElement to create a new HTML structure.
   • The script loops 10,000 times, creating a new <div> element with a class of "container", another <div> element inside it, and an <a> element within the inner <div>.
   • The script then appends this new structure to a document.createDocumentFragment object and appends that fragment to the #appendedItems container.
2. cloneNode
   • This test case uses cloneNode to clone an existing HTML structure from the DOM.
   • The script first queries for an element with class "container" using document.querySelector.
   • It then loops 10,000 times, cloning the selected element and making changes to its child elements (specifically, changing the text content of the <a> element).
   • The cloned element is then appended to a document.createDocumentFragment object and appended to the #appendedItems container.

Library: Document Fragment

The document.createDocumentFragment object is used in both test cases. This object allows us to create a new, empty HTML structure that can be appended to other elements without actually creating new DOM nodes. This can improve performance by reducing the number of DOM node creations.

Special JS Feature/Syntax

There are no special JavaScript features or syntaxes mentioned in this benchmark. However, it's worth noting that using document.createDocumentFragment is a common pattern in JavaScript testing and benchmarking, as it allows for efficient manipulation of HTML structures without creating new DOM nodes.

Pros and Cons of Approaches

1. createElement
   • Pros: creates new elements from scratch, can be more intuitive for some developers.
   • Cons: may be slower due to the overhead of creating new DOM nodes.
2. cloneNode
   • Pros: faster, as it reuses existing DOM nodes.
   • Cons: may require additional setup and maintenance, such as updating child element references.

Other Considerations

When benchmarking JavaScript performance, it's essential to consider factors beyond just the approach used. Some other considerations include:

• HTML structure complexity: The complexity of the HTML structure being created or cloned can significantly impact performance.
• Node count: The number of DOM nodes being created or appended can also affect performance.
• Browser support: Different browsers may have varying levels of support for certain JavaScript features or APIs.

Alternatives

If you're looking for alternative approaches to benchmarking JavaScript performance, consider:

• V8 Benchmark: A benchmark suite developed by Google that tests various aspects of JavaScript performance.
• SpiderMonkey Benchmark: A benchmark suite developed by Mozilla that tests various aspects of JavaScript performance on the SpiderMonkey engine.
• JSPerf: A benchmarking tool specifically designed for testing JavaScript performance.