Benchmark: querySelectorAll vs getElementsByTagName iteration 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'); for(let i = 0; i < allDivs.length; i++);
getElementsByTagName
const allDivs = document.getElementsByTagName('div'); for(let i = 0; i < allDivs.length; i++);

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:

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the provided benchmark.

**Benchmark Overview**

The benchmark is designed to compare the performance of two JavaScript methods for selecting elements from an HTML document: `querySelectorAll` and `getElementsByTagName`. The test creates multiple `<div>` elements in an HTML string, which serves as the input data for these selection methods.

**Options Compared**

Two options are being compared:

1. **querySelectorAll**: This method returns a NodeList (a live HTMLCollection) containing all matching elements, or null if no matches were found.
2. **getElementsByTagName**: This method also returns a collection of DOM elements that match the specified element name.

**Pros and Cons**

* `querySelectorAll` has several advantages:
	+ It's more flexible than `getElementsByTagName`, as it allows selecting elements based on a CSS selector (e.g., `div > p`).
	+ It returns a live NodeList, which can be iterated over using a for loop or other methods.
	+ It's generally faster and more efficient than `getElementsByTagName`.
* However, `querySelectorAll` has some limitations:
	+ It only works on elements that support CSS selectors (i.e., most modern browsers).
	+ It may return null if no matching elements are found.

On the other hand, `getElementsByTagName` is simpler and more widely supported:

* Pros:
	+ It's a well-established method that works across older browsers.
	+ It doesn't require CSS selectors or specific element names.
* Cons:
	+ It returns an HTMLCollection (not a live NodeList), which can be less convenient to work with.
	+ It's generally slower and less efficient than `querySelectorAll`.

**Library**

None are used in this benchmark. The methods being compared are built-in JavaScript methods.

**Special JS Feature/Syntax**

There is no special feature or syntax being tested in this benchmark. However, the use of CSS selectors (in `querySelectorAll`) assumes a modern browser that supports them.

**Other Alternatives**

If you need to select elements in older browsers or require more advanced selection capabilities, consider using:

1. **`querySelector`**: This method is similar to `querySelectorAll`, but returns only the first matching element.
2. **`getElementsByClassName`**, `getElementsByAttribute`, and other DOM methods: These can be used for more specific selections.

Keep in mind that browser support and performance may vary depending on the alternative method chosen.

Related benchmarks:

querySelectorAll vs getElementsByTagName iteration 2 (version: 0)

Comparing performance of: querySelectorAll vs getElementsByTagName

Created: 3 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByTagName

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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