Benchmark: Add Class to existing className vs. setAttribute vs. classList

HTML Preparation code:

<div id="foo" class="class1 class2"></div>

Tests:

classListVar
var element = document.getElementById("foo"); var i = 1000; var classListTemp = element.classList; while (i--) { classListTemp.add("class3"); }
setAttribute
var element = document.getElementById("foo"); var i = 1000; while (i--) { element.setAttribute("class", "class1 class2 class3"); }
classList
var element = document.getElementById("foo"); var i = 1000; while (i--) { element.classList.add("class3"); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
classListVar
setAttribute
classList

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one month ago):

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark on the MeasureThat.net website. The benchmark compares three approaches for adding a class to an existing HTML element: `classList`, `setAttribute`, and setting a `className` attribute directly.

**Approaches Compared**

1. **classList**: This approach uses the `classList` property of the DOM element, which allows you to add classes dynamically.
2. **setAttribute**: This approach uses the `setAttribute()` method to set the `class` attribute of the element.
3. **setClassname**: Although not explicitly mentioned in the JSON, this is likely an alternative approach, and it's worth noting that the MeasureThat.net website might use a specific implementation or variant of this approach.

**Pros and Cons of Each Approach**

1. **classList**:
	* Pros: More modern and efficient, as it leverages the optimized `classList` property.
	* Cons: Requires support for CSS classes in HTML5, which not all browsers may have.
2. **setAttribute**:
	* Pros: Wide browser support, as it's a standard DOM method.
	* Cons: May be slower due to the additional overhead of parsing and setting an attribute.
3. **setClassname**: (Assumed alternative approach)
	* Pros: Might offer better performance or different behavior than `classList` in specific scenarios.
	* Cons: Not explicitly mentioned in the JSON, so its exact implementation is unknown.

**Library Usage**

None of the provided approaches rely on external libraries. However, if you were to use a library like jQuery or Zepto for DOM manipulation, it might provide an additional layer of complexity and performance impact.

**Special JS Features/Syntax**

The `classList` property relies on CSS classes in HTML5, which is a relatively modern feature. Not all browsers support this feature, so you should test your code across different browser versions.

**Alternative Approaches**

If you're interested in exploring alternative approaches for adding a class to an element, consider the following:

1. **CSS**: Using CSS stylesheets or inline styles might be more efficient than JavaScript methods.
2. **DOM mutations**: Other DOM mutation methods, like `appendChild()` or `insertAdjacentHTML()`, could potentially offer better performance.
3. **native Web APIs**: Newer web APIs, such as the Web APIs for CSS and HTML5, might provide optimized solutions for adding classes to elements.

Keep in mind that each approach has its trade-offs, and the best solution will depend on your specific use case, browser requirements, and performance constraints.

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser/OS: Chrome 121 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
classListVar	6764.5 Ops/sec
setAttribute	17282.3 Ops/sec
classList	6252.0 Ops/sec

Related benchmarks:

Add Class to existing className vs. setAttribute vs. classList (version: 4)

Comparing performance of: classListVar vs setAttribute vs classList

Created: 6 years ago by: Registered User

Jump to the latest result

classListVar

setAttribute

classList

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one month ago):