Benchmark: getElementsByClassName, querySelector

HTML Preparation code:

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

Tests:

getElementsByClassName
document.getElementsByClassName("test");
querySelector
document.querySelector(".test")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementsByClassName
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.

Let's break down the provided JSON data and explain what's being tested, compared, and evaluated in the MeasureThat.net JavaScript microbenchmark.

**Benchmark Definition**

The benchmark definition is represented by two test cases:

1. `getElementsByClassName`: This test case uses the `document.getElementsByClassName()` method to retrieve elements with a specific class name.
2. `querySelector`: This test case uses the `document.querySelector()` method to select an element based on its CSS selector.

**Script and HTML Preparation Codes**

The script preparation code is empty, which means that no custom JavaScript code is executed before running the benchmark. However, the HTML preparation code includes a simple `<div>` element with the class name "test".

**Options Compared**

In this benchmark, two options are compared:

1. `getElementsByClassName`: This method retrieves elements by their class names.
2. `querySelector`: This method selects an element based on its CSS selector.

**Pros and Cons of Each Approach**

Here's a brief overview of the pros and cons of each approach:

* **getElementsByClassName**:
	+ Pros: Efficient for retrieving multiple elements with the same class name, can be used to select elements in a document.
	+ Cons: Can be slower than `querySelector` when only one element is expected, returns an HTMLCollection which can be slow for large datasets.
* **querySelector**:
	+ Pros: Faster and more efficient than `getElementsByClassName`, returns a single DOM element or null if not found.
	+ Cons: May require additional CSS styles to make the selector accurate, can be slower for complex selectors.

**Library and Purpose**

Neither of these methods relies on any external libraries. They are built-in methods provided by the Document Object Model (DOM) in JavaScript.

**Special JS Features/Syntax**

There is no special JavaScript feature or syntax being tested here. The benchmark only focuses on comparing two fundamental DOM methods.

**Other Alternatives**

If you needed to compare other DOM methods, such as:

* `getElementById()`: Retrieves an element by its ID attribute.
* `getElementsByAttribute()`: Retrieves elements based on a specific attribute value.
* `querySelectorAll()`: Selects all elements that match a CSS selector.
* `Element.contains()`: Checks if an element contains another element.

Keep in mind that these alternatives would require additional test cases and preparation codes to accurately compare their performance.

Related benchmarks:

getElementsByClassName, querySelector (version: 0)

Comparing performance of: getElementsByClassName vs querySelector

Created: 8 years ago by: Guest

Jump to the latest result

getElementsByClassName

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):