Benchmark: querySelector vs getElementsByClassName with proper utilization

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

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36

Browser/OS: Chrome 143 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelectorAll	12714961.0 Ops/sec
getElementsByClassName	36421944.0 Ops/sec

Autogenerated LLM Summary (model gemma2:9b, generated one year ago):

LLMs can make mistakes. Check important info.

This benchmark compares the performance of two methods for selecting HTML elements: `document.querySelectorAll` and `document.getElementsByClassName`.

**Options Compared:**

* **`document.querySelectorAll(".test")`**: This method uses CSS selectors to select all elements with the class "test". It returns a NodeList, which is an array-like object of the selected elements.
* **`document.getElementsByClassName("test")`**: This method selects all elements with the specified class name ("test"). It returns a live HTMLCollection, meaning it updates automatically if the DOM changes.

**Pros and Cons:**

* **`querySelectorAll`**: 
    * **Pros**: More versatile as it supports CSS selectors, allowing for more complex and powerful selection criteria. Can be used to select elements based on attributes, relationships, etc.
    * **Cons**: Generally slower than `getElementsByClassName` for simple class-based selections.

* **`getElementsByClassName`**: 
    * **Pros**: Faster and more lightweight when selecting elements based solely on their class name.
    * **Cons**: Less versatile as it only supports class name selection.

**Other Considerations:**

* **Performance impact:** In this specific benchmark, `getElementsByClassName` is significantly faster than `querySelectorAll`. This is likely due to the simplicity of the selection criteria (selecting elements with a single class).

**Alternatives:**

* **Direct element access:** If you know the exact position or index of the element you need, you can access it directly using its corresponding index in the DOM.
* **JavaScript libraries:** Libraries like jQuery provide streamlined methods for selecting and manipulating HTML elements, often offering performance optimizations.

It's important to choose the appropriate method based on your specific needs and the complexity of your selection criteria.

Related benchmarks:

querySelector vs getElementsByClassName with proper utilization (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>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gemma2:9b, generated one year ago):