Benchmark: QuerySelector vs QuerySelectorAll vs getElementsByClassName

HTML Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
querySelectorAll
getElementsByClassName

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the benchmark.

**What is being tested?**

The benchmark is testing three different methods to select elements from an HTML document: `document.querySelector()`, `document.querySelectorAll()`, and `document.getElementsByClassName()`. The goal is to compare their performance in selecting an element with a specific class (`".test"`).

**Options compared**

The options being compared are:

1. **`document.querySelector()`**: This method returns the first element that matches the specified selector. In this case, it's searching for an element with the exact class `".test"`.
2. **`document.querySelectorAll()`**: This method returns a list of all elements that match the specified selector. Again, in this case, it's searching for elements with the exact class `".test"`, but instead of returning just one element, it returns multiple elements.
3. **`document.getElementsByClassName()`**: This method returns a live HTMLCollection of all elements with the specified class name.

**Pros and cons of each approach**

1. **`document.querySelector()`**:
	* Pros: Fast and efficient, as it only searches for the first matching element.
	* Cons: May return `null` if no element is found, which can lead to additional checks or error handling.
2. **`document.querySelectorAll()`**:
	* Pros: Returns all matching elements, which can be useful in certain scenarios. It also returns a NodeList, which is an HTMLCollection that supports indexing and iteration.
	* Cons: May be slower than `querySelector` because it needs to search the entire DOM for all matches.
3. **`document.getElementsByClassName()`**:
	* Pros: Returns all elements with the specified class name, which can be useful in certain scenarios. It's also relatively fast compared to `querySelectorAll`.
	* Cons: Returns an HTMLCollection, which is not as flexible or powerful as a NodeList.

**Library and purpose**

In this benchmark, none of the methods require any additional libraries. They are all built-in methods of the Document object in JavaScript.

**Special JS feature or syntax**

There isn't any special feature or syntax being tested here. The code is straightforward and uses only standard JavaScript and DOM manipulation techniques.

**Other alternatives**

If you're looking for alternative methods to select elements, some other options include:

* `document.querySelectorAll()`: This method is similar to `querySelectorAll()` but returns an array of all matching elements instead of a NodeList.
* `querySelector` with CSS selectors: You can use CSS selectors with the `querySelector` method to select elements based on their class, id, or attribute values. For example: `document.querySelector('.test')`.
* Other libraries like jQuery or DOM manipulation libraries may provide alternative methods for selecting elements.

In conclusion, this benchmark is testing the performance of three common methods for selecting elements from an HTML document: `document.querySelector()`, `document.querySelectorAll()`, and `document.getElementsByClassName()`. The results can help developers choose the best approach depending on their specific use case.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36

Browser/OS: Chrome 78 on Mac OS X 10.13.6

View result in a separate tab

Test name	Executions per second
querySelector	3575971.0 Ops/sec
querySelectorAll	1347252.8 Ops/sec
getElementsByClassName	5042755.5 Ops/sec

Related benchmarks:

QuerySelector vs QuerySelectorAll vs getElementsByClassName (version: 0)

Comparing performance of: querySelector vs querySelectorAll vs getElementsByClassName

Created: 5 years ago by: Guest

Jump to the latest result

querySelector

querySelectorAll

getElementsByClassName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):