Benchmark: querySelector vs getElementsByClassName [0] with extra

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: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelector	2796675.8 Ops/sec
getElementsByClassName	2427959.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks!

The provided JSON represents a benchmark test between two methods for selecting an HTML element: `document.querySelector()` and `document.getElementsByClassName()`. The goal is to measure which method performs better in terms of execution speed.

**Options compared:**

1. **`document.querySelector()`**: This method uses the CSS selector syntax to select elements. It's a more modern and efficient approach, introduced in ECMAScript 5 (ES5).
2. **`document.getElementsByClassName()`**: This method uses a string that contains the class name of the element being targeted. It's an older method, introduced before ES5.

**Pros and Cons:**

1. **`document.querySelector()`**:
	* Pros: More efficient, flexible, and modern.
	* Cons: Requires knowledge of CSS selectors, which can be complex.
2. **`document.getElementsByClassName()`**:
	* Pros: Simpler to understand, as it only requires the class name.
	* Cons: Less efficient than `querySelector()`, especially for larger datasets.

When comparing these two methods, we need to consider factors such as:

* The complexity of the CSS selector or class names used.
* The size of the dataset being queried.
* The browser's performance and optimization.

**Library usage:**

There is no explicit library mentioned in the benchmark definition. However, it's worth noting that both `querySelector()` and `getElementsByClassName()` rely on the DOM (Document Object Model) and are part of the browser's built-in functionality.

**Special JS feature/syntax:**

The benchmark doesn't use any special JavaScript features or syntax beyond what's required for the tests. It only focuses on comparing the performance of two basic methods.

Now, let's take a look at how these tests might be prepared and executed:

To prepare the test, you would create an HTML file that includes a `<div>` element with a specific class name (e.g., `.test`). Then, in your JavaScript code, you would use either `document.querySelector()` or `document.getElementsByClassName()` to select this element.

For example, using `querySelector()`:
```javascript
const div = document.querySelector('.test');
```
And using `getElementsByClassName()`:
```javascript
const div = document.getElementsByClassName('test')[0];
```
The benchmark is likely executed multiple times in a loop, and the execution time is measured using a tool like `console.time()` or `performance.now()`. The results are then recorded and compared to determine which method performs better.

**Alternatives:**

If you're interested in exploring alternative methods for selecting elements, here are a few options:

* **`document.querySelectorAll()`**: This method returns an HTMLCollection of all elements that match the specified CSS selector. It's similar to `querySelector()`, but it returns multiple matches instead of just one.
* **`document.querySelectorAll()`** (Chrome only): This method is similar to `querySelector()` but is optimized for performance and can return multiple matches.
* **`DOMTokenList`**: This API provides a more modern way to manipulate class lists on elements. It's supported in modern browsers and can be used instead of `getElementsByClassName()`.
* **`CSSOM` APIs**: The CSS Object Model (CSSOM) provides an API for working with CSS rules and stylesheets. It can be used to select elements based on CSS selectors, but it requires more complex setup.

Keep in mind that these alternatives might not provide a direct comparison to the original benchmark, as they introduce additional complexity or performance optimizations.

Related benchmarks:

querySelector vs getElementsByClassName [0] with extra (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 5 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):