Benchmark: getElementById vs getElementsByClassName aasa

HTML Preparation code:

<div id="a" class="a">d</div>

Tests:

getElementById
let el = document.getElementById('a'); el.innerHTML = 'abc';
getElementsByClassName
let el = document.getElementsByClassName('a')[0]; el.innerHTML = 'abc';
querySelector
let el = document.querySelector('.a'); el.innerHTML = 'abc';

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
getElementsByClassName
querySelector

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:120.0) Gecko/20100101 Firefox/120.0

Browser/OS: Firefox 120 on Windows

View result in a separate tab

Test name	Executions per second
getElementById	246330.3 Ops/sec
getElementsByClassName	230006.6 Ops/sec
querySelector	225569.7 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmarking setup and explain what's being tested, compared, and the pros/cons of each approach.

**Benchmark Definition**

The benchmark is designed to compare the performance of three different methods for selecting an HTML element by its class name: `getElementsByClassName`, `querySelector`, and `getElementById`.

**Options Compared**

1. **getElementsByClassName**: This method returns a live HTMLCollection, which is an array-like object containing all elements with the specified class name.
2. **querySelector**: This method returns the first element that matches the specified CSS selector.
3. **getElementById**: This method returns the element with the specified id.

**Pros and Cons of Each Approach**

1. **getElementsByClassName**
	* Pros:
		+ Works even if there are multiple elements with the same class name.
		+ Can be used to select elements that have a specific class name in combination with other attributes (e.g., `div class="header"`)
	* Cons:
		+ Returns an array-like object, which can be slower than returning a single element.
		+ Can return multiple elements if there are multiple elements with the same class name.
2. **querySelector**
	* Pros:
		+ Faster than `getElementsByClassName` since it returns a single element.
		+ More flexible and powerful for complex CSS selectors.
	* Cons:
		+ Only returns the first matching element, which can lead to slower performance if there are multiple matches.
3. **getElementById**
	* Pros:
		+ Fastest since it directly accesses the DOM element by its id.
		+ Returns a single element, reducing the number of elements that need to be processed.
	* Cons:
		+ Only works for elements with a unique id.
		+ Can lead to slower performance if there are multiple elements with the same id.

**Other Considerations**

1. **Library and Purpose**: The `querySelector` method uses the W3C querySelector API, which is part of the DOM4 specification. This API provides a standardized way to select elements using CSS selectors.
2. **Special JS Feature or Syntax**: There are no special JavaScript features or syntax used in this benchmark.

**Alternatives**

Other methods for selecting HTML elements include:

1. `getElementsByTagName`: Returns an array-like object containing all elements with the specified tag name.
2. `querySelectorAll`: Returns a NodeList of all elements that match the specified CSS selector.
3. `addEventListener` and `removeEventListener`: Used to attach and detach event listeners from elements, respectively.

Note that the performance differences between these methods can vary depending on the specific use case and browser implementation.

Related benchmarks:

getElementById vs getElementsByClassName aasa (version: 1)

a

Comparing performance of: getElementById vs getElementsByClassName vs querySelector

Created: 2 years ago by: Registered User

Jump to the latest result

getElementById

getElementsByClassName

querySelector

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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