Benchmark: this-is-a-test-2

HTML Preparation code:

<div class="test">
  <span class="my-test"> Test </span>
</div>

Tests:

className
document.getElementsByClassName(".my-test")[0]
querySelector
document.querySelectorAll(".my-test")[0]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
className
querySelector

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

I'd be happy to help you understand the JavaScript microbenchmark on MeasureThat.net.

**What is being tested?**

The provided benchmark tests two different approaches to selecting an HTML element by its class name:

1. `document.getElementsByClassName(".my-test")[0]`
2. `document.querySelectorAll(".my-test")[0]`

In both cases, the goal is to retrieve the first element that matches a specific class name (`"my-test"`).

**Options compared**

The benchmark compares two approaches:

* **`getElementsByClassName()`**: This method returns a live HTMLCollection of all elements with the specified class name. In this case, it's assumed to return only one element since we're selecting the first one with `[0]`.
* **`querySelector()`**: This method allows you to select an element by its CSS selector syntax. Here, it's used with a single class selector (`".my-test"`).

**Pros and Cons of each approach**

1. **`getElementsByClassName()`**:
	* Pros: Generally faster since it doesn't require the DOM parser.
	* Cons: Can be slower for large sets of elements or when used extensively in a loop, as it returns a live collection that can cause unnecessary recalculations.
2. **`querySelector()`**:
	* Pros: Faster and more efficient than `getElementsByClassName()` for most use cases.
	* Cons: Requires the DOM parser to parse the CSS selector syntax, which can add overhead.

**Library used**

Neither of these methods requires a separate library beyond what's included with JavaScript itself. However, if you're interested in exploring other libraries or tools that provide similar functionality, some popular options include:

* `CSS Selectors` (built-in)
* **Sizzle.js**: A lightweight CSS selector engine for JavaScript
* **QuerySelector.js**: A polyfill for the `querySelector` method

**Special JS feature or syntax**

In this benchmark, there is no special JavaScript feature or syntax being used beyond what's standard in modern JavaScript. Both methods are widely supported across browsers and should work without any additional setup.

**Other alternatives**

If you're looking to optimize your code further, consider the following alternatives:

* Use a CSS selector library like Sizzle.js or QuerySelector.js to improve performance for complex selections.
* Implement a custom caching mechanism to reduce the overhead of repeated DOM queries.
* Consider using a virtual DOM library to minimize the number of actual DOM mutations.

Keep in mind that these optimizations may not significantly impact your use case unless you're working with extremely large datasets or performance-critical code.

Related benchmarks:

this-is-a-test-2 (version: 0)

Comparing performance of: className vs querySelector

Created: 4 years ago by: Guest

Jump to the latest result

className

querySelector

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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