Benchmark: querySelector vs getElementsByClassName 23313

HTML Preparation code:

<div class="test"></div>

Tests:

querySelector
document.querySelector(".test")
getElementsByClassName
document.getElementsByClassName("test")[0]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Browser/OS: Firefox 78 on Linux

View result in a separate tab

Test name	Executions per second
querySelector	2848282.8 Ops/sec
getElementsByClassName	2658272.5 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!

**What is being tested?**

The provided benchmark tests the performance difference between two DOM query methods:

1. `document.querySelector(".test")`
2. `document.getElementsByClassName("test")[0]`

These methods are used to retrieve elements from a HTML document.

**Options compared**

The two options are compared, which are:

* `querySelector` (or `.querySelector()`)
* `getElementsByClassName` (or `getElementsByClassName()`)

**Pros and Cons of each approach:**

* `querySelector`:
	+ Pros:
		- More efficient, as it stops at the first match
		- Can be used to select elements based on multiple selectors
	+ Cons:
		- May not work with older browsers (before Firefox 4)
		- Requires an ID or class selector in the query string
* `getElementsByClassName`:
	+ Pros:
		- Works with all browsers, including older ones
		- Can be used to select elements based on multiple classes
	+ Cons:
		- Returns a live HTMLCollection, which can be slower and less efficient than a single element

**Library usage**

In the benchmark, `document` is being used, which is a part of the DOM (Document Object Model) API. The DOM provides a way to interact with and manipulate an HTML document programmatically.

**Special JS feature or syntax**

There are no special JavaScript features or syntax mentioned in this benchmark. However, it's worth noting that `querySelector` was introduced in Firefox 4 and became widely adopted in modern browsers.

**Other alternatives**

If you want to test other DOM query methods, you can consider using:

* `document.getElementsByTagName()` (which returns a live HTMLCollection)
* `document.getElementById()` (which returns the first element with the specified ID)
* `querySelectorAll()` (which returns a NodeList of all elements matching the selector)

Keep in mind that each method has its own trade-offs and use cases, and this benchmark is specifically testing `querySelector` against `getElementsByClassName`.

I hope this explanation helps!

Related benchmarks:

querySelector vs getElementsByClassName 23313 (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 3 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

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):