Benchmark: [Fixed] querySelectorAll vs. getElementsByClassName

HTML Preparation code:

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

Tests:

querySelectorAll
document.querySelectorAll(".test")
getElementsByClassName
document.getElementsByClassName("test")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelectorAll
getElementsByClassName

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.212 Safari/537.36

Browser/OS: Chrome 90 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelectorAll	1895121.0 Ops/sec
getElementsByClassName	4151404.2 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

The provided JSON represents a benchmark test on MeasureThat.net, which compares the performance of two DOM selection methods in JavaScript: `querySelectorAll` and `getElementsByClassName`. These methods are used to retrieve elements from an HTML document based on their class name or attribute values.

**Methods being compared:**

1. **`querySelectorAll`**: This method returns a NodeList (or an Array-like object) containing all elements that match the specified selector. The selector is a CSS query that can be expressed as a string.
2. **`getElementsByClassName`**: This method returns a collection of DOM elements with the specified class name.

**Options being compared:**

In this benchmark, two options are being compared:

* `querySelectorAll`: which selects all elements based on their class name (`.test`)
* `getElementsByClassName`: which also selects all elements based on their class name (`.test`)

**Pros and Cons of each approach:**

1. **`querySelectorAll`**:
	* Pros:
		+ More flexible than `getElementsByClassName`, as it can select elements based on any CSS selector.
		+ Can be used to target elements with specific attributes or pseudo-classes.
	* Cons:
		+ May be slower for large datasets, as it needs to scan the entire DOM.
		+ Can be more complex to use, especially for beginners.
2. **`getElementsByClassName`**:
	* Pros:
		+ Faster than `querySelectorAll` for small to medium-sized datasets.
		+ Easier to use and understand, as it's a simple method that only returns elements with the specified class name.
	* Cons:
		+ Less flexible than `querySelectorAll`, as it can only select elements based on their class name.

**Library used:**

In this benchmark, no specific library is mentioned. However, both methods rely on the browser's built-in DOM API to access and manipulate elements in an HTML document.

**Special JS feature or syntax:**

None of the methods being compared require any special JavaScript features or syntax that are not standard in modern browsers. They are widely supported by most JavaScript engines and can be used in a wide range of development environments.

**Other alternatives:**

If you need to compare performance between different DOM selection methods, here are some other alternatives you might consider:

* **`getElementsByTagName`**: This method returns an array of elements with the specified tag name.
* **`getElementById`**: This method returns the element with the specified ID attribute.
* **`querySelector`** and **`querySelectorAll`** (with different selectors): These methods can be used to select elements based on various CSS selectors, such as class names, IDs, or attributes.

Keep in mind that each of these alternatives has its own pros and cons, and may not always be the best choice for your specific use case.

Related benchmarks:

[Fixed] querySelectorAll vs. getElementsByClassName (version: 0)

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: 3 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByClassName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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