Benchmark: querySelector vs getElementsByClassName

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 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:146.0) Gecko/20100101 Firefox/146.0

Browser/OS: Firefox 146 on Linux

View result in a separate tab

Test name	Executions per second
querySelector	3410582.2 Ops/sec
getElementsByClassName	4004591.2 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmark test case on the MeasureThat.net website, which compares the performance of two DOM query methods: `querySelector` and `getElementsByClassName`. Let's break down what's being tested:

**What is being compared?**

* `querySelector`: A method used to select elements from an HTML document using a CSS selector.
* `getElementsByClassName`: A method used to retrieve all elements with a specific class name.

**Options compared:**

The benchmark tests the execution speed of these two methods, specifically when selecting an element by its class name (`".test"`).

**Pros and Cons:**

* **`querySelector`**:
	+ Pros:
		- More concise and readable code.
		- Fewer options to choose from (single selector), which reduces computational overhead.
	+ Cons:
		- May require more computational resources to resolve the selector, especially when dealing with complex queries.
* `getElementsByClassName`:
	+ Pros:
		- Can be more efficient for certain use cases, such as when working with a large number of elements with the same class name.
	+ Cons:
		- More verbose code and options to choose from (multiple class names), which can increase computational overhead.

**Library:**

In this benchmark, `getElementsByClassName` uses an internal implementation that relies on the DOM's method calls to retrieve elements. The exact library or framework used is not specified.

**Special JS feature or syntax:**

None mentioned in the provided JSON. However, it's worth noting that both methods use the `document` object and HTML document structure.

**Other alternatives:**

If you need alternative approaches for selecting DOM elements, consider:

1. `querySelectorAll`: Similar to `getElementsByClassName`, but returns a NodeList instead of an array.
2. `getElementsByTagName`: Returns a list of all elements with a specific tag name (e.g., `div`, `p`, etc.).
3. `getElementById`: Retrieves an element by its ID attribute.
4. Using CSS selectors with `document.querySelector` or `querySelectorAll`.

Keep in mind that each approach has its own trade-offs and performance characteristics, which may affect the overall efficiency of your application.

In conclusion, this benchmark provides a simple and clear comparison between two DOM query methods, allowing users to understand the relative performance differences between `querySelector` and `getElementsByClassName`.

Related benchmarks:

querySelector vs getElementsByClassName (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 8 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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