Benchmark: querySelector vs getElementsByClassName 2

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: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36

Browser/OS: Chrome 67 on Mac OS X 10.13.6

View result in a separate tab

Test name	Executions per second
querySelector	4499129.5 Ops/sec
getElementsByClassName	4246871.5 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark compares two approaches to selecting an element by class name in HTML documents: `querySelector` and `getElementsByClassName`. The goal is to determine which method is faster for a given use case.

**Options Compared**

Two options are compared:

1. **`document.querySelector('.test')`**: This method uses the CSS selector syntax to select an element with the class `test`.
2. **`document.getElementsByClassName('test')[0]`**: This method returns a live HTMLCollection of all elements with the class `test`, and we're only interested in the first element (index 0).

**Pros and Cons**

1. **`querySelector`**:
	* Pros: More efficient, less memory usage, better performance.
	* Cons: Less flexible, requires exact CSS selector syntax, may not work for older browsers.
2. **`getElementsByClassName`**:
	* Pros: More flexible, works with older browsers, can be used to select multiple elements.
	* Cons: Less efficient, more memory usage, slower performance.

**Library and Purpose**

None are explicitly mentioned in this benchmark.

**Special JS Feature or Syntax**

No special JavaScript features or syntax are used in this benchmark. The focus is on the two DOM methods for selecting elements by class name.

**Other Alternatives**

If you need to select an element based on multiple criteria, you can use `querySelectorAll` (all elements matching a CSS selector) or `querySelectorAll` with `^=` (elements starting with a specific string).

For more complex selections, consider using a library like Sizzle.js (a CSS selector engine for JavaScript) or cheerio (a jQuery-like library for parsing and manipulating HTML documents).

Keep in mind that browser support may vary depending on the implementation. Always test your code across different browsers and versions to ensure compatibility.

MeasureThat.net is a valuable resource for comparing performance and finding the most efficient solutions for common DOM-related tasks. By running these benchmarks, developers can make informed decisions about their code and optimize it for better performance.

Related benchmarks:

querySelector vs getElementsByClassName 2 (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 6 years ago by: Guest

Jump to the latest result

querySelector

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):