Benchmark: querySelectorAll vs getElementsByTagName iteration - better

HTML Preparation code:

<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<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'); for (let div of allDivs) { div; }
getElementsByTagName
const allDivs = document.getElementsByTagName('div'); for (let div of allDivs) { 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: 4 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36

Browser/OS: Chrome 86 on Linux

View result in a separate tab

Test name	Executions per second
querySelectorAll	62494.4 Ops/sec
getElementsByTagName	68040.6 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 explanation of the provided benchmark.

**Benchmark Overview**

The benchmark compares two methods for selecting HTML elements: `document.querySelectorAll('div')` and `document.getElementsByTagName('div')`. The goal is to determine which method is more efficient, specifically in terms of iteration performance.

**Options Compared**

The benchmark tests two options:

1. **querySelectorAll**: This method uses a CSS selector to select all elements that match the specified type (in this case, 'div'). It returns a NodeList, which is an ordered collection of nodes that can be traversed using standard array methods.
2. **getElementsByTagName**: This method takes a string argument representing the tag name and returns a NodeList containing only elements with that tag name.

**Pros and Cons**

* **querySelectorAll**:
	+ Pros: More flexible and powerful than `getElementsByTagName`, as it allows for more complex selectors and can be used to select elements based on their class, ID, or other attributes.
	+ Cons: May have performance overhead due to the complexity of the selector, especially for large selections. Additionally, some browsers may optimize this method less than others.
* **getElementsByTagName**:
	+ Pros: Often faster and more optimized than `querySelectorAll`, as it's a simpler method that only returns elements with a specific tag name.
	+ Cons: Less flexible and powerful than `querySelectorAll`, as it doesn't allow for complex selectors or attribute matching.

**Library and Syntax**

Neither of these methods uses any libraries. They are built-in DOM methods provided by modern browsers.

**Special JS Features/Syntax**

The benchmark does not use any special JavaScript features or syntax beyond the standard DOM methods mentioned earlier.

**Benchmark Preparation Code**

The HTML preparation code consists of a series of 11 `<div>` elements, which is likely used to create a large enough dataset for the benchmark. The script preparation code is empty, suggesting that the focus is on comparing the two DOM methods rather than executing any additional JavaScript code.

**Other Alternatives**

If you were to compare these methods in a different context or with different options, some alternative approaches might include:

* Using `querySelector` instead of `querySelectorAll`, which would select only the first element matching the specified type.
* Using a library like jQuery to simplify DOM selection and manipulation.
* Using a more modern approach, such as using `Array.from()` and `Element.matches()` to achieve similar results.

However, for this specific benchmark, comparing `querySelectorAll` and `getElementsByTagName` provides a straightforward comparison of two common DOM methods.

Related benchmarks:

querySelectorAll vs getElementsByTagName iteration - better (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):