Benchmark: querySelector vs getElementsByClassName

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

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what is being tested.

**Benchmark Definition JSON**

The provided JSON represents a JavaScript microbenchmark named "querySelector vs getElementsByClassName". This benchmark compares the performance of two methods: `document.querySelectorAll()` and `document.getElementsByClassName()`. The benchmark aims to measure which method is faster for selecting elements with a specific class name (`test`) in HTML.

**Script Preparation Code and Html Preparation Code**

The provided script preparation code is empty, which means that no custom JavaScript code is executed before running the test. However, the Html Preparation Code contains a single `<div>` element with the class `test`, which will be used to select elements for both methods being tested.

**Individual Test Cases**

There are two individual test cases:

1. **querySelectorAll**: This test case measures the performance of selecting elements using `document.querySelectorAll()`. The benchmark definition is a simple call to `document.querySelectorAll()` with the CSS selector `.test`.
2. **getElementsByClassName**: This test case measures the performance of selecting elements using `document.getElementsByClassName()`. The benchmark definition is a simple call to `document.getElementsByClassName()` with the class name `test`.

**Library and its Purpose**

There is no specific library mentioned in the provided code. However, both `document.querySelectorAll()` and `document.getElementsByClassName()` are built-in methods in JavaScript that work on HTML documents.

**Special JS Features or Syntax**

Neither of the test cases uses any special JavaScript features or syntax beyond what is normally available in standard JavaScript.

**Options Compared**

The two options being compared are:

1. **querySelectorAll**: This method returns a NodeList of elements that match the specified CSS selector.
2. **getElementsByClassName**: This method returns an array-like object containing all elements with the specified class name.

**Pros and Cons of Each Approach**

Here are some pros and cons of each approach:

*   **querySelectorAll**
    *   Pros:
        *   More flexible and powerful than `getElementsByClassName` for selecting elements.
        *   Can handle more complex selectors, including attribute-based selectors.
    *   Cons:
        *   May be slower than `getElementsByClassName` due to the overhead of evaluating CSS selectors.
*   **getElementsByClassName**
    *   Pros:
        *   Faster and more lightweight than `querySelectorAll`.
        *   More straightforward and simple to use, especially for basic class-based selections.
    *   Cons:
        *   Less flexible and powerful than `querySelectorAll`, as it only supports class names.

**Other Considerations**

When choosing between `querySelectorAll` and `getElementsByClassName`, consider the following factors:

*   **Complexity of selection**: If you need to select elements with complex CSS selectors, `querySelectorAll` may be a better choice.
*   **Performance requirements**: If you're working on a performance-critical application and need the fastest possible solution, `getElementsByClassName` might be a better option.
*   **Readability and maintainability**: If you're writing code that needs to be readable and maintainable, using `querySelectorAll` with a simple CSS selector can make your code more concise and easier to understand.

**Alternatives**

Other alternatives for selecting elements in JavaScript include:

1.  **CSSOM Traversal API**: This API provides a more powerful and flexible way of traversing the DOM, allowing you to select elements based on various criteria such as class names, IDs, attributes, and more.
2.  **Sizzle.js** (or other CSS selector libraries): These libraries provide an extension of the `querySelectorAll` method that allows for more complex CSS selectors.

Keep in mind that each approach has its pros and cons, and the best choice depends on your specific use case and requirements.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:101.0) Gecko/20100101 Firefox/101.0

Browser/OS: Firefox 101 on Windows

View result in a separate tab

Test name	Executions per second
querySelectorAll	1203575.8 Ops/sec
getElementsByClassName	5156936.0 Ops/sec

Related benchmarks:

querySelector vs getElementsByClassName (version: 0)

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: 6 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByClassName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):