Benchmark: queryselector vs getelementbyid with classes and ids

HTML Preparation code:

<div class="container">
  <div class="header"></div>
    <div class="content">
    <div class="title"></div>
    <div class="text">
    	<div id="testElement"></div>
    </div>
  </div>
  <div class="footer"></div>
</div>

Tests:

querySelector
var el = document.querySelector('#testElement'); var className = el.className;
getElementById
var el = document.getElementById('testElement'); var className = el.className;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementById

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 dive into the details of this benchmark.

**What is being tested?**

The provided JSON represents a JavaScript microbenchmark that compares two different ways to retrieve an element from an HTML document: `querySelector` and `getElementById`. Both methods are used to access an element with a specific class name (`className`) and ID (`id`).

**Options compared**

There are two options compared:

1. **`querySelector`**: This method uses CSS selectors to select the desired element. It's more flexible than `getElementById`, as it allows you to target elements based on their classes, IDs, tag names, and other attributes.
2. **`getElementById`**: This method uses a simple ID-based lookup to retrieve an element. It's faster for retrieving an element by its unique ID but less flexible than `querySelector`.

**Pros and Cons**

* `querySelector`:
	+ Pros: more flexible, works with multiple classes and IDs, can be used in conjunction with other CSS selectors.
	+ Cons: potentially slower than `getElementById`, as it requires parsing the HTML document to determine which element matches the selector.
* `getElementById`:
	+ Pros: faster for retrieving an element by its unique ID, as it doesn't require parsing the HTML document.
	+ Cons: less flexible, only works with a single ID per element.

**Library**

In this benchmark, there is no specific library used. The `querySelector` and `getElementById` methods are built-in JavaScript APIs.

**Special JS feature or syntax**

There is no special JavaScript feature or syntax used in this benchmark. However, it's worth noting that the `querySelector` method was introduced in ECMAScript 5 (ES5) as a replacement for `getElementsByTagName`.

**Other alternatives**

If you're interested in exploring alternative methods to retrieve elements from an HTML document, here are some options:

* **`getElementsByClassName`**: This method returns a list of all elements with the specified class name.
* **`querySelectorAll`**: Similar to `querySelector`, but returns a NodeList of all matching elements instead of a single element.
* **`getElementsByTagName`**: Returns a NodeList of all elements with the specified tag name.

These alternatives offer different trade-offs in terms of flexibility, performance, and compatibility across browsers.

Latest run results:

Run details: (Test run date: 3 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

Browser/OS: Chrome 126 on Linux

View result in a separate tab

Test name	Executions per second
querySelector	3684098.0 Ops/sec
getElementById	7844322.5 Ops/sec

Related benchmarks:

queryselector vs getelementbyid with classes and ids (version: 0)

Comparing performance of: querySelector vs getElementById

Created: 3 months ago by: Guest

Jump to the latest result

querySelector

getElementById

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):