Benchmark: getElementById vs querySelector ID vs getElementsByClassName vs querySelectorAll ver2

HTML Preparation code:

<div id="test_element_id" class="test_element_class"></div>

Tests:

getElementById
var el = document.getElementById('test_element_id');
querySelector
var el = document.querySelector('#test_element_id');
getElementsByClassName
var el = document.getElementsByClassName('test_element_class')[0];
querySelectorAll
var el = document.querySelectorAll('.test_element_class')[0];
querySelector class
var el = document.querySelector('.test_element_class');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
querySelector
getElementsByClassName
querySelectorAll
querySelector class

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:122.0) Gecko/20100101 Firefox/122.0

Browser/OS: Firefox 122 on Windows

View result in a separate tab

getElementById

7.7M/s

querySelector

4.1M/s

getElementsByClassName

3.9M/s

querySelector class

3.7M/s

querySelectorAll

1.8M/s

View exact numbers

Test name	Executions per second
✓ getElementById	7,691,434 Ops/sec
querySelector	4,139,755 Ops/sec
getElementsByClassName	3,872,344 Ops/sec
querySelector class	3,722,568 Ops/sec
querySelectorAll	1,773,960 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll explain the benchmark in detail.

**What is being tested?**

The provided JSON represents a JavaScript microbenchmarking test case, specifically comparing the performance of four different methods to select an element from a HTML document: `getElementById`, `querySelector` with an ID selector, `getElementsByClassName` with a class selector, and `querySelectorAll` with a class selector. The test also includes a variant that selects elements by their class using only `querySelector`.

**Options being compared**

Here's a brief overview of each option:

1. **getElementById**: This method takes an element ID as a string parameter and returns the first element in the document whose ID matches the specified value.
2. **querySelector**: This method takes a CSS selector (e.g., `#test_element_id`) as a string parameter and returns the first element that matches the selection criteria.
3. **getElementsByClassName**: This method takes one or more class names as string parameters and returns an array of elements that have at least one of the specified classes.
4. **querySelectorAll**: This method takes a CSS selector (e.g., `.test_element_class`) as a string parameter and returns a NodeList containing all elements that match the selection criteria.

**Pros and Cons**

Here's a brief summary of each option:

* **getElementById**:
	+ Pros: Simple, widely supported, and fast.
	+ Cons: Only works for single-element IDs, can lead to slower performance if there are multiple elements with the same ID (caching).
* **querySelector**:
	+ Pros: Flexible, supports more complex selectors, and is faster than `getElementById` for multiple element IDs.
	+ Cons: Can be slower for simple selectors compared to `getElementById`.
* **getElementsByClassName**:
	+ Pros: Allows selecting elements based on classes, can be used with multiple class names.
	+ Cons: Returns an array of elements, which can lead to slower performance if the array is large. Also, it has a higher memory overhead due to the array returned.
* **querySelectorAll**:
	+ Pros: Supports complex selectors and returns a NodeList containing all matching elements.
	+ Cons: Can be slower than other methods for simple selections, as it needs to scan the entire document.

**Library and purpose**

In this benchmark, none of the libraries are explicitly mentioned. However, `document.querySelector` and `document.querySelectorAll` are part of the HTML5 DOM API, which is a built-in JavaScript library provided by modern browsers.

**Special JS features or syntax**

There's no special JS feature or syntax used in this benchmark, as it only involves standard JavaScript methods and CSS selectors.

**Other alternatives**

If you're looking for alternative methods to select elements, here are some options:

* **getElementsByIndex**: Similar to `getElementsByClassName`, but takes an index instead of classes.
* **querySelectorAll` with `nodeList` iterator: Instead of using the entire NodeList returned by `querySelectorAll`, you can use a `nodeList` iterator to iterate over the elements, which can be more memory-efficient.

Keep in mind that these alternatives may have different performance characteristics and usage scenarios compared to the methods being tested in this benchmark.

getElementById vs querySelector ID vs getElementsByClassName vs querySelectorAll ver2 (version: 0)

Comparing performance of: `getElementById vs querySelector vs getElementsByClassName vs querySelectorAll vs querySelector class`

Created: 2 years ago by: Guest

Go to the latest result

getElementById

querySelector

getElementsByClassName

querySelectorAll

querySelector class

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

getElementById vs querySelector ID vs getElementsByClassName vs querySelectorAll ver2 (version: 0)

Comparing performance of: getElementById vs querySelector vs getElementsByClassName vs querySelectorAll vs querySelector class

Created: 2 years ago by: Guest

Go to the latest result

getElementById

querySelector

getElementsByClassName

querySelectorAll

querySelector class

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `getElementById vs querySelector vs getElementsByClassName vs querySelectorAll vs querySelector class`