Benchmark: querySelectorAll vs. getElementsByClassName bug patch

HTML Preparation code:

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

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

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of MeasureThat.net and explore what's being tested in this benchmark.

**Benchmark Overview**

The benchmark is designed to compare the performance of two DOM selection methods: `querySelectorAll` and `getElementsByClassName`. The test case uses an HTML element with a class attribute named "test".

**Options Compared**

Two options are compared:

1. **`document.querySelectorAll(".test")`**: This method returns a NodeList containing all elements that match the specified CSS selector, ".test". It's a more modern and efficient approach to selecting DOM elements.
2. **`document.getElementsByClassName("test")`**: This method returns an HTMLCollection containing all elements that match the specified class name, "test". Although this method was widely used in the past, it has been deprecated since ECMAScript 5 (2009) and replaced by `querySelectorAll`.

**Pros and Cons**

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

Pros:

* More efficient than `getElementsByClassName` (less CPU cycles)
* Less prone to false positives (e.g., selecting elements with other class names)
* Compatible with modern browsers

Cons:

* May have slower performance in older browsers that don't support it
* Requires a CSS selector, which can be less intuitive for beginners

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

Pros:

* Widely supported across older browsers (IE 8+, Firefox 3.5+)
* Can be used with inline styles or attributes that contain class names

Cons:

* More CPU-intensive and slower than `querySelectorAll`
* Prone to false positives if the element has other class names
* Depreciated since ECMAScript 5, so it's not recommended for new development.

**Library Usage**

None of the test cases use a library or any external dependencies.

**Special JS Feature/Syntax**

There is no special JavaScript feature or syntax being tested in this benchmark. The focus is solely on comparing the performance of two DOM selection methods.

**Other Alternatives**

If you want to create similar benchmarks, consider testing other DOM selection methods, such as:

* `document.querySelector(".test")` (a more concise alternative to `querySelectorAll`)
* `document.getElementsByTagName("div")[0].classList.contains("test")` (using the `contains` method with an element's class list)
* `document.querySelectorAll("[class='test']")` (selecting elements by attribute)

Keep in mind that these alternatives may have different performance characteristics and should be tested accordingly.

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/83.0.4103.97 Safari/537.36

Browser/OS: Chrome 83 on Windows

View result in a separate tab

Test name	Executions per second
querySelectorAll	1274191.2 Ops/sec
getElementsByClassName	2580084.2 Ops/sec

Related benchmarks:

querySelectorAll vs. getElementsByClassName bug patch (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 26 days ago):