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

Test name	Executions per second
getElementById	7691434.0 Ops/sec
querySelector	4139755.0 Ops/sec
getElementsByClassName	3872343.8 Ops/sec
querySelectorAll	1773960.2 Ops/sec
querySelector class	3722568.0 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.

Related benchmarks:

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

Jump 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):