Benchmark: querySelectorAll vs getElementsByTagName [for loop]

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 += 1) { console.log(allDivs[i]); }
getElementsByTagName
const allDivs = document.getElementsByTagName('div'); for (let i = 0; i < allDivs.length; i += 1) { console.log(allDivs[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 break down what's being tested in the provided benchmark:

**What is being tested:**

The benchmark is comparing two approaches to select all HTML elements with the tag name "div":

1. `document.querySelectorAll('div')`
2. `document.getElementsByTagName('div')`

Both methods are used to retrieve a NodeList of elements that match the specified selector.

**Options compared:**

The two options being compared are:

* `querySelectorAll` (also known as `querySelectorAll()`): This method uses CSS selectors to select elements and returns a NodeList. It's more flexible than `getElementsByTagName`, as it can be used with different types of selectors, such as class names or ID values.
* `getElementsByTagName`: This method directly selects elements by their tag name and returns an HTMLCollection (in older browsers). It's less flexible than `querySelectorAll`, but often faster for simple selections.

**Pros and cons:**

* **`querySelectorAll`**:
	+ Pros: More flexible, supports CSS selectors, faster in modern browsers.
	+ Cons: Can be slower for very large lists of elements due to the need to parse CSS selectors.
* **`getElementsByTagName`**:
	+ Pros: Often faster for simple selections, as it can use native DOM methods to retrieve elements directly.
	+ Cons: Less flexible than `querySelectorAll`, limited to selecting by tag name only.

In general, if you're working with complex HTML structures or need to select elements based on CSS selectors, `querySelectorAll` is a better choice. However, for simple selections and performance-critical code, `getElementsByTagName` might be faster.

**Library usage:**

* Both methods use the Document Object Model (DOM) of the browser to interact with the document.
* No external libraries are used in this benchmark.

**Special JS features or syntax:**

There's no mention of any special JavaScript features or syntax being tested in this benchmark. It appears to be a straightforward comparison of two DOM selection methods.

**Alternatives:**

Other methods for selecting elements include:

* `querySelector` (a simpler version of `querySelectorAll`, which can only select by CSS selector)
* `document.querySelector`
* `Element.querySelectorAll` (a method that returns an array of matches instead of a NodeList)

Keep in mind that the choice of selection method depends on your specific use case and performance requirements.

Related benchmarks:

querySelectorAll vs getElementsByTagName [for loop] (version: 0)

Comparing performance of: querySelectorAll vs getElementsByTagName

Created: 5 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):