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

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

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!

**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.

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 2 months ago):