Benchmark: querySelectorAll vs getElementsByClassName - timing

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_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.2 Safari/605.1.15

Browser/OS: Safari 14 on Mac OS X 10.15.6

View result in a separate tab

Test name	Executions per second
querySelectorAll	2741081.0 Ops/sec
getElementsByClassName	4967335.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark test case, specifically comparing the performance of `document.querySelectorAll()` and `document.getElementsByClassName()`. The benchmark is designed to measure the execution time of these two functions on different browsers and devices.

**What are being tested?**

* **`document.querySelectorAll()`**: This function returns a NodeList containing all elements that match the specified CSS selector.
* **`document.getElementsByClassName()`**: This function returns an HTMLCollection of all elements with the specified class name.

**Options comparison**

The benchmark compares two options:

1. `querySelectorAll()`: Uses a selector to search for matching elements, which can be more efficient than using class names.
2. `getElementsByClassName()`: Uses class names to find matching elements, which can be slower due to the potential for more elements being matched.

**Pros and Cons**

* **`querySelectorAll()`**
	+ Pros:
		- Can be faster since it only searches for matching elements with a single selector.
		- More flexible, as selectors can match multiple classes and attributes.
	+ Cons:
		- May not work as expected if the CSS selector is incorrect or ambiguous.
* **`getElementsByClassName()`**
	+ Pros:
		- Guaranteed to find all elements with the specified class name, regardless of other classes or attributes.
	+ Cons:
		- May be slower due to the potential for more elements being matched.

**Library usage**

In this benchmark, no libraries are used. However, it's worth noting that some libraries (e.g., jQuery) might provide similar functionality with their own implementations.

**Special JavaScript features or syntax**

The benchmark uses CSS selectors and class names, which are standard in HTML and CSS. There is no special JavaScript feature or syntax being tested here.

**Other alternatives**

For this specific use case, other alternatives to `querySelectorAll()` and `getElementsByClassName()` might include:

* **`document.querySelector()`**: Similar to `querySelectorAll()`, but returns a single element instead of a NodeList.
* **`CSS selectors`**: Using CSS selectors with the `:class` pseudo-class can achieve similar results without using JavaScript.

**Benchmark preparation code**

The provided HTML code `<div class="test"></div>` is used as a test case container. The script preparation code is empty, which means no additional setup or initialization is required for this benchmark.

Related benchmarks:

querySelectorAll vs getElementsByClassName - timing (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):