Benchmark: querySelector, getElementsByClassName

HTML Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The current benchmark compares the performance of two HTML query methods: `querySelector` and `getElementsByClassName`.

**Tested Options**

The benchmark tests two options:

1. **`document.querySelector('.test')`**: This method is used to select an element from the DOM using a CSS selector.
2. **`document.getElementsByClassName('test')`**: This method is used to get all elements with a specific class name.

**Pros and Cons of Each Approach**

**`document.querySelector('.test')`:**

Pros:

* More efficient than `getElementsByClassName` since it only returns the first matching element.
* Less overhead due to the use of CSS selectors, which are optimized by browsers.
* Can be more flexible when used with attribute selectors or pseudo-classes.

Cons:

* May not return all elements with the specified class name if there are multiple occurrences.
* Requires a CSS selector syntax, which can be error-prone if not properly formatted.

**`document.getElementsByClassName('test')`:**

Pros:

* Returns all elements with the specified class name, making it useful for cases where you need to find all elements with a particular attribute.
* Does not require a CSS selector syntax, making it easier to write and debug.

Cons:

* Can be slower than `querySelector` due to the overhead of getting all matching elements.
* Returns an HTMLCollection (an array-like object) that needs to be iterated over or converted to an array.

**Library and Purpose**

There is no specific library mentioned in the benchmark. However, both methods use the DOM API, which is a built-in JavaScript API provided by web browsers for interacting with the Document Object Model (DOM).

**Special JS Feature/Syntax**

The `querySelector` method uses a CSS selector syntax, which is a feature introduced in ECMAScript 2009 (ES5). This allows you to select elements based on their CSS styles, classes, IDs, and attributes. The CSS selector syntax provides a more expressive way of selecting elements than the older `getElementsByTagName` method.

**Other Alternatives**

If you need to perform similar operations as `querySelector` and `getElementsByClassName`, other alternatives include:

* Using the `HTMLElement.prototype.matches()` method (introduced in ECMAScript 2017) for CSS selector-based selection.
* Utilizing a library like jQuery or Cheerio, which provide additional selectors and utility functions for working with DOM elements.

Overall, the choice between `document.querySelector('.test')` and `document.getElementsByClassName('test')` depends on your specific use case and performance requirements. If you need to select only one element, `querySelector` is likely a better option. However, if you need to find all elements with a particular class name, `getElementsByClassName` might be more suitable.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.96 Safari/537.36

Browser/OS: Chrome 58 on Windows

View result in a separate tab

Test name	Executions per second
querySelector	1324171.6 Ops/sec
getElementsByClassName	2225786.2 Ops/sec

Related benchmarks:

querySelector, getElementsByClassName (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 6 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):