Benchmark: querySelector and getElementsByClassName performance

HTML Preparation code:

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Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querrySelector
getElementsByClassName

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Overview**

The provided benchmark, "querySelector and getElementsByClassName performance", tests the performance of two common DOM query methods in JavaScript: `document.querySelector()` and `document.getElementsByClassName()`. The benchmark creates a complex HTML structure with nested elements to simulate real-world scenarios where these queries are used.

**Options Compared**

Two options are compared:

1. **`document.querySelector()`**: This method takes a string argument representing the CSS selector and returns the first element that matches the selector.
2. **`document.getElementsByClassName()`**: This method takes a string argument representing the class name and returns an array of elements with the specified class.

**Pros and Cons**

Here are some pros and cons of each option:

* `document.querySelector()`:
	+ Pros:
		- More precise control over element selection.
		- Can be more efficient for modern browsers that have improved selector engine.
	+ Cons:
		- May be slower for older browsers or in cases where multiple elements match the selector.
* `document.getElementsByClassName()`:
	+ Pros:
		- Generally faster than `querySelector` due to its simplicity and less computational overhead.
	+ Cons:
		- Less precise control over element selection, as it returns all elements with the specified class name, regardless of their position or context.

**Library Usage**

Both options use the DOM API, which is a built-in JavaScript library. The DOM (Document Object Model) provides an interface for working with HTML documents and represents the structure of a document using objects.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax mentioned in this benchmark. However, it's worth noting that `document.querySelector()` was introduced in ECMAScript 5 (ES5), while `document.getElementsByClassName()` has been available since Netscape Navigator 4.x ( released in 1996).

**Alternative Approaches**

If you're interested in optimizing DOM queries or exploring alternative approaches, here are some alternatives:

1. **CSS Selectors**: Modern browsers have improved CSS selector engines, making it possible to use native CSS selectors for element selection.
2. **QuerySelectorAll()**: This method returns all elements that match the specified CSS selector, allowing you to retrieve multiple elements at once.
3. **MutationObserver**: This API allows you to observe changes to the DOM and react to them in real-time.

Keep in mind that these alternatives may have different performance characteristics or require additional setup, so it's essential to evaluate their suitability for your specific use case.

I hope this explanation helps you understand the benchmarking process on MeasureThat.net!

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Linux; Android 12) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.102 Safari/537.36

Browser/OS: Chrome 98 on Android

View result in a separate tab

Test name	Executions per second
querrySelector	1277707.9 Ops/sec
getElementsByClassName	2993944.8 Ops/sec

Related benchmarks:

querySelector and getElementsByClassName performance (version: 0)

Comparing performance of: querrySelector vs getElementsByClassName

Created: 3 years ago by: Registered User

Jump to the latest result

querrySelector

getElementsByClassName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):