Benchmark: querySelectorAll vs getElementsByTagName 2

HTML Preparation code:

<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>

Tests:

querySelectorAll
const allDivs = document.querySelectorAll('div');
getElementsByTagName
const allDivs = document.getElementsByTagName('div');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelectorAll
getElementsByTagName

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks!

**Benchmark Description**

The provided JSON represents a benchmark test case that compares two approaches to retrieve all HTML elements with the tag name "div": `document.querySelectorAll('div')` and `document.getElementsByTagName('div')`.

**Options Compared**

Two options are being compared:

1. **querySelectorAll**: This method uses the QuerySelector API, which provides a more efficient way of selecting elements based on CSS selectors. It returns a NodeList containing all matching elements.
2. **getElementsByTagName**: This method uses the older `getElementsByName()` API and returns an HTMLCollection containing all elements with the specified tag name.

**Pros and Cons**

* **querySelectorAll**:
	+ Pros: More efficient, more flexible (supports CSS selectors), and generally faster than `getElementsByTagName`.
	+ Cons: Requires support for the QuerySelector API, which might not be available in older browsers.
* **getElementsByTagName**:
	+ Pros: Widely supported across different browsers, doesn't require the QuerySelector API.
	+ Cons: Less efficient, less flexible (only works with exact tag names), and slower than `querySelectorAll`.

In modern JavaScript environments, `querySelectorAll` is generally recommended due to its efficiency and flexibility.

**Library Used**

Neither of these methods relies on a specific library. They are built-in browser APIs.

**Special JS Feature or Syntax**

The QuerySelector API (used by `querySelectorAll`) uses a CSS selector syntax, which allows for more flexible and expressive selections. For example: `document.querySelectorAll('div div')` would match all elements with both the tag name "div" and at least one child element.

**Other Considerations**

* Both methods have a different behavior when used with `Element.prototype.slice.call()`: `querySelectorAll` returns an HTMLCollection, while `getElementsByTagName` returns an array-like object. This can lead to inconsistencies in certain situations.
* In modern browsers, `querySelectorAll` is generally faster and more efficient than `getElementsByTagName`. However, the actual performance difference may vary depending on the specific use case and browser implementation.

**Alternatives**

If you're looking for alternative methods to retrieve all elements with a specific tag name, consider using:

1. **QuerySelector API**: A modern and flexible way of selecting elements based on CSS selectors.
2. **CSS Selectors**: You can use plain CSS selectors in your JavaScript code to select elements. For example: `document.querySelectorAll('div')`.
3. **Sizzle.js** or **PureCSS**: These are libraries that provide a more efficient and flexible alternative to the QuerySelector API.

Keep in mind that these alternatives might have different performance characteristics and may not be supported by all browsers.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Safari/537.36

Browser/OS: Chrome 106 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelectorAll	1690412.4 Ops/sec
getElementsByTagName	4742898.5 Ops/sec

Related benchmarks:

querySelectorAll vs getElementsByTagName 2 (version: 0)

Comparing performance of: querySelectorAll vs getElementsByTagName

Created: 4 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByTagName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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