Benchmark: className vs. classList v2

HTML Preparation code:

<div id="foo" class="test"></div>

Tests:

className
var element = document.getElementById("foo"); var i = 1000; while (i--) { if (element.className.indexOf("test") > -1) { element.className = "bar"; } else { element.className = "test"; } }
classList
var element = document.getElementById("foo"); var i = 1000; while (i--) { if (element.classList.contains("test")) { element.classList.add("bar"); } else { element.classList.add("test"); } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
className
classList

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases.

**Benchmark Definition:**

The benchmark measures the performance of two different approaches to update an HTML element's class names:

1. `className`: This approach uses the `indexOf` method to check if the element's current class name contains the string "test". If it does, it replaces the class name with "bar".
2. `classList`: This approach uses the `contains` and `add` methods of the `classList` property to achieve the same result.

**Script Preparation Code:**

There is no script preparation code provided, which means that the benchmark starts from a clean slate without any pre-existing scripts or variables.

**Html Preparation Code:**

The HTML preparation code creates an HTML element with the id "foo" and an initial class name of "test".

**Individual Test Cases:**

There are two test cases:

1. `className`:
```javascript
var element = document.getElementById("foo");
var i = 1000;
while (i--) {
  if (element.className.indexOf("test") > -1) {
    element.className = "bar";
  } else {
    element.className = "test";
  }
}
```
This test case uses the `indexOf` method to check if the element's class name contains the string "test".

2. `classList`:
```javascript
var element = document.getElementById("foo");
var i = 1000;
while (i--) {
  if (element.classList.contains("test")) {
    element.classList.add("bar");
  } else {
    element.classList.add("test");
  }
}
```
This test case uses the `contains` and `add` methods of the `classList` property to achieve the same result.

**Library:**

In both test cases, the `document.getElementById` method is used to retrieve the HTML element with the id "foo". This method is a part of the DOM (Document Object Model) API, which is built into most modern browsers.

**Special JS Features/Syntax:**

There are no special JavaScript features or syntax mentioned in the benchmark definition. Both test cases use standard JavaScript methods and properties.

**Pros and Cons:**

Here are some pros and cons of each approach:

1. `className`:
	* Pros:
		+ Wide support across browsers
		+ Simple and easy to understand
	* Cons:
		+ Slow performance due to the use of the `indexOf` method, which has to iterate over the entire class name string
2. `classList`:
	* Pros:
		+ Faster performance compared to the `className` approach
		+ More efficient use of resources
	* Cons:
		+ Requires modern browsers that support the `classList` property
		+ May require additional setup or polyfills for older browsers

**Other Alternatives:**

If you need alternative approaches, here are a few options:

1. Using a library like jQuery, which provides an efficient way to update class names using its `.toggleClass()` method.
2. Implementing a custom solution that uses a more efficient algorithm, such as using a regular expression or a custom string manipulation function.

However, the `classList` approach is generally considered the best choice for modern browsers, and the `className` approach can be used as a fallback for older browsers that don't support `classList`.

Related benchmarks:

className vs. classList v2 (version: 0)

Comparing performance of: className vs classList

Created: 7 years ago by: Guest

Jump to the latest result

className

classList

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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