Benchmark: querySelectorAll vs. getElementsByClassName (multiple class test)

HTML Preparation code:

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

Tests:

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

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

LLMs can make mistakes. Check important info.

I'd be happy to help you understand what's being tested in the provided benchmark.

**What is being tested?**

MeasureThat.net is testing two JavaScript methods: `querySelectorAll` and `getElementsByClassName`. These methods are used to retrieve elements from an HTML document. The benchmark is specifically designed to compare their performance on a desktop Linux system with Chrome 91 browser, using multiple class test.

**Options being compared**

The two options being compared are:

1. `querySelectorAll`: This method returns a NodeList containing all elements that match the specified CSS selector.
2. `getElementsByClassName`: This method returns an HTMLCollection of elements whose class attribute matches the specified value.

**Pros and Cons:**

- **`querySelectorAll`**
	+ Pros:
		- More flexible, as it can be used to select elements based on any valid CSS selector (not just class names).
		- Can be faster for complex selections.
	+ Cons:
		- May be slower for simple selections with many elements.
		- Has a slightly higher memory overhead due to the NodeList's dynamic nature.

- **`getElementsByClassName`**
	+ Pros:
		- Faster for simple selections with few or no elements.
		- Simpler and more predictable behavior.
	+ Cons:
		- Less flexible, as it only returns elements whose class attribute matches the specified value.
		- May be slower for complex selections.

**Library usage**

The `getElementsByClassName` method uses the `HTMLCollection` interface, which is a built-in JavaScript interface. The `querySelectorAll` method uses the ` NodeList` interface, also a built-in JavaScript interface.

**Special JS feature or syntax**

There is no special JavaScript feature or syntax being used in this benchmark. However, it's worth noting that the `querySelectorAll` and `getElementsByClassName` methods are part of the W3C DOM specification and have been implemented by most modern browsers since their introduction.

**Other alternatives**

If you're looking for alternative libraries or methods to achieve similar functionality, consider:

1. `document.querySelector`: Similar to `querySelectorAll`, but returns a single element (not a collection).
2. `CSS Selectors API`: A more powerful and flexible way to select elements based on CSS selectors.
3. `Sizzle.js`: A lightweight, fast CSS selector engine.

Keep in mind that using alternative libraries or methods might not always provide a significant performance improvement over the built-in methods, but they can offer additional features and flexibility.

Related benchmarks:

querySelectorAll vs. getElementsByClassName (multiple class test) (version: 0)

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: 5 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByClassName

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):