Benchmark: querySelectorAll vs. getElementsByClassName x 10

HTML Preparation code:

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

querySelectorAll
document.querySelectorAll(".test")
getElementsByClassName
document.getElementsByClassName("test")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelectorAll
getElementsByClassName

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36

Browser/OS: Chrome 87 on Windows

View result in a separate tab

Test name	Executions per second
querySelectorAll	302421.2 Ops/sec
getElementsByClassName	930762.9 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data and explain what's being tested, compared, and their pros and cons.

**Benchmark Definition**

The benchmark definition consists of two test cases:

1. `document.querySelectorAll(".test")`
2. `document.getElementsByClassName("test")`

These two test cases are comparing the performance of two DOM querying methods: `querySelectorAll` and `getElementsByClassName`.

**Comparison**

Both test cases are comparing the number of executions per second for each method, measured in `ExecutionsPerSecond`. The benchmark is running on a Windows 10 desktop device with Chrome 87 browser.

**Options Compared**

The options being compared are:

* `document.querySelectorAll(".test")`
* `document.getElementsByClassName("test")`

These two methods have different behavior and use cases:

* `querySelectorAll` returns a NodeList containing all elements that match the specified CSS selector. It's more efficient for selecting multiple elements, but it may return fewer results than expected if the matching element is not unique.
* `getElementsByClassName` returns an HTMLCollection of all elements with the specified class name. It's less efficient for selecting multiple elements and may be slower due to its more extensive DOM traversal.

**Pros and Cons**

Here are some pros and cons of each approach:

* `querySelectorAll`
	+ Pros:
		- More efficient for selecting multiple elements.
		- Returns a NodeList, which is more type-safe than HTMLCollection.
	+ Cons:
		- May return fewer results if the matching element is not unique.
		- Not supported in older browsers.
* `getElementsByClassName`
	+ Pros:
		- Supports older browsers that don't support `querySelectorAll`.
		- Returns an HTMLCollection, which can be useful for certain use cases.
	+ Cons:
		- Less efficient than `querySelectorAll` for selecting multiple elements.
		- May be slower due to its more extensive DOM traversal.

**Library and Purpose**

The two libraries being used in these test cases are:

* `document.querySelectorAll` and `document.getElementsByClassName`: These are built-in methods of the Document Object Model (DOM) API in JavaScript. They're used for selecting elements within an HTML document.
* None: There is no additional library being used in this benchmark.

**Special JS Feature or Syntax**

None of the code snippets provided use any special JavaScript features or syntax that's not widely supported.

**Alternatives**

Other alternatives to these methods include:

* `querySelector` and `querySelectorAll`
* CSS selectors (e.g., `document.querySelector('.test')`)
* Other DOM querying methods, such as `getElementsByTagName`, `getElementById`

These alternatives may have different performance characteristics or use cases than the two methods being compared in this benchmark.

Related benchmarks:

querySelectorAll vs. getElementsByClassName x 10 (version: 0)

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: 4 years ago by: Guest

Jump to the latest result

querySelectorAll

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):