Benchmark: querySelector vs getElementsByClassName My

HTML Preparation code:

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

Tests:

querySelector
document.querySelector(".test")
getElementsByClassName
document.getElementsByClassName(".test")[0]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Windows

View result in a separate tab

Test name	Executions per second
querySelector	9306032.0 Ops/sec
getElementsByClassName	5172567.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested, compared, and some considerations.

**Benchmark Definition**
The benchmark defines two test cases: `querySelector` and `getElementsByClassName`. These are JavaScript methods used to select elements in HTML documents.

**What is being tested?**

* `document.querySelector('.test')`: This method selects the first element with the class `test`.
* `document.getElementsByClassName('test')[0]`: This method returns an array of elements with the class `test` and returns the first element from that array.

**Options compared**

The benchmark is comparing two approaches to select elements:

1. **querySelector**: A modern, faster way to select elements using a CSS selector syntax.
2. **getElementsByClassName**: An older way to select elements by class name, which was the only method available before `querySelector` was introduced in modern browsers.

**Pros and Cons**

* **querySelector**:
	+ Pros: Faster, more efficient, and widely supported across modern browsers. It's also more flexible than `getElementsByClassName`.
	+ Cons: Requires CSS selectors to be used, which can add complexity.
* **getElementsByClassName**:
	+ Pros: Simpler to use and more forgiving for older browsers that don't support `querySelector`. It's also more flexible when dealing with elements without a class attribute.
	+ Cons: Slower and less efficient than `querySelector`.

**Library usage**

In the benchmark, `document` is used as the root element of the HTML document. There are no external libraries being used.

**Special JS features or syntax**

There are none mentioned in this specific benchmark. However, it's worth noting that other benchmarks might use newer JavaScript features like async/await, Promises, or modern language constructs like arrow functions or destructuring.

**Other alternatives**

For selecting elements, you can also use other methods like:

* `querySelectorAll`: Similar to `querySelector`, but returns a NodeList with all matching elements.
* `document.querySelector~` and `document.querySelectorAll~`: These use a substring matching approach for partial matches.
* Other libraries like jQuery or Vanilla-Extract.

Keep in mind that the best method for your specific use case depends on factors like browser support, performance requirements, and complexity.

Related benchmarks:

querySelector vs getElementsByClassName My (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 4 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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