Benchmark: querySelector vs get First Element By Class Name

HTML Preparation code:

<div class="test"></div>
<div class="test2"></div>
<div class="test3"></div>
<div class="test4"></div>

Tests:

querySelector
document.querySelector(".test")
getElementsByClassName[0]
document.getElementsByClassName(".test")[0]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName[0]

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares two approaches to select an element by class name: `document.querySelector()` and `document.getElementsByClassName()[0]`. Both methods are used to retrieve the first element with the specified class name from a HTML document.

**Options Compared**

There are only two options being compared:

1. **`document.querySelector(".test")`**: This method uses the `querySelector` function, which returns the first element that matches the specified selector (in this case, an element with the class "test").
2. **`document.getElementsByClassName("test")[0]`**: This method uses the `getElementsByClassName` function to retrieve all elements with the specified class name and then returns the first one in the resulting array.

**Pros and Cons of Each Approach**

1. **`document.querySelector(".test")`**:
	* Pros:
		+ More concise and expressive syntax.
		+ Handles more complex selectors, including attribute values and pseudo-classes.
		+ Returns the first matching element, which is what we want in this benchmark.
	* Cons:
		+ May be slower than `getElementsByClassName` for very large numbers of elements or deeply nested HTML structures.
2. **`document.getElementsByClassName("test")[0]`**:
	* Pros:
		+ Can return multiple elements if there are multiple elements with the specified class name, whereas `querySelector` would stop at the first match.
	* Cons:
		+ Requires more code to get the desired result (by indexing into the array returned by `getElementsByClassName`).
		+ May be slower than `querySelector` due to the overhead of creating and searching an array of elements.

**Library Used**

In this benchmark, no specific JavaScript library is used beyond the standard DOM APIs (`document`, `querySelector`, `getElementsByClassName`). However, if we were using a more advanced library like jQuery, it would likely provide an alternative implementation for these methods.

**Special JS Features or Syntax**

None are mentioned in the provided code snippet. If any special features or syntax were involved (e.g., ES6 classes, Promises, async/await), they would not be relevant to this specific benchmark.

**Alternatives**

Other alternatives for selecting elements by class name might include:

* Using `document.querySelector()` with a more complex selector (e.g., `.test > div`, `[data-test="text"]`)
* Using `getElementsByClassName()` in combination with other DOM methods (e.g., `querySelectorAll()`, `getElementsByTagName()`)
* Using CSS selectors with the `querySelector()` method
* Using a library like jQuery or React's `useRef`/`useCallback` hooks to handle element selection and manipulation.

Keep in mind that these alternatives might not be as straightforward or efficient as the original implementation compared in this benchmark.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36

Browser/OS: Chrome 83 on Windows

View result in a separate tab

Test name	Executions per second
querySelector	1670700.0 Ops/sec
getElementsByClassName[0]	1092603.1 Ops/sec

Related benchmarks:

querySelector vs get First Element By Class Name (version: 0)

Comparing performance of: querySelector vs getElementsByClassName[0]

Created: 4 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName[0]

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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