Benchmark: querySelector vs getElementsByClassName with proper utilization

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: 5 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36

Browser/OS: Chrome 143 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelectorAll	12714961.0 Ops/sec
getElementsByClassName	36421944.0 Ops/sec

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

LLMs can make mistakes. Check important info.

Let's dive into the details of this benchmark.

**What is being tested?**

The benchmark compares two methods for selecting HTML elements on a web page:

1. `document.querySelectorAll(".test")`
2. `document.getElementsByClassName("test")`

In other words, it tests how long it takes to retrieve all elements with a specific class name (`"test"`).

**What options are compared?**

There are only two test cases in this benchmark:

1. **querySelectorAll**: This method uses the `querySelectorAll` API, which returns a NodeList of all elements that match the specified selector (in this case, an element with class `"test"`).
2. **getElementsByClassName**: This method uses the `getElementsByClassName` API, which also returns a HTMLCollection of all elements that have the specified class name.

**Pros and Cons:**

Here's a brief summary:

* **querySelectorAll**:
	+ Pros: Returns a NodeList (an array-like object), easy to work with.
	+ Cons: Might be slower due to its more general-purpose nature.
* **getElementsByClassName**:
	+ Pros: Specifically designed for class name selection, might be faster as a result.
	+ Cons: Returns an HTMLCollection, which is not as flexible as a NodeList.

**Library and purpose**

No external libraries are used in this benchmark. The two methods being compared are part of the standard JavaScript API.

**Special JS feature or syntax**

There's no special JavaScript feature or syntax involved in this benchmark. Both methods use standard DOM APIs.

**Alternatives**

If you need to select multiple elements with specific class names, here are some alternatives:

* Use `querySelectorAll` and specify a selector that targets all classes (e.g., `.test ~ .another-class`). This method is more flexible than using separate calls to `getElementsByClassName`.
* If performance is crucial, consider using a library like Sizzle or jQuery, which can optimize selection operations.
* For modern browsers, you might also use the CSS selector API (`document.querySelectorAll("...")`) with more advanced selectors (e.g., attribute selectors).

That's it! I hope this explanation helps software engineers understand the pros and cons of these two methods.

Related benchmarks:

querySelector vs getElementsByClassName with proper utilization (version: 0)

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: 4 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByClassName

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):