Benchmark: getElementById vs querySelector - multi level

HTML Preparation code:

<div id="testElement">
  <div id="subElement"></div>
  <div id="subElement2"></div>
  <div id="subElement3"></div>
  <div id="subElement4"></div>
  <div id="subElement5"></div>
  <div id="subElement6"></div>
  <div id="subElement7"></div>
  <div id="subElement8"></div>
  <div id="subElement9"></div>
  <div id="subElement10"></div>
</div>
<div id="randomElement">
  <div id="randomSubElement"></div>
  <div id="randomSubElement2"></div>
  <div id="randomSubElement3"></div>
  <div id="randomSubElement4"></div>
  <div id="randomSubElement5"></div>
  <div id="randomSubElement6"></div>
  <div id="randomSubElement7"></div>
  <div id="randomSubElement8"></div>
  <div id="randomSubElement9"></div>
  <div id="randomSubElement10"></div>
</div>

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
querySelector
swag

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 world of JavaScript microbenchmarks!

**Benchmark Overview**

The provided benchmark measures the performance difference between three methods to retrieve an element by its ID: `getElementById`, `querySelector`, and `swag` (note: `swag` is not a standard JavaScript method, so I'll assume it's some kind of proprietary or experimental implementation).

**Options Compared**

1. **getElementById**: This method directly retrieves the first element with the specified ID from the DOM.
2. **querySelector**: This method uses CSS selectors to retrieve an element that matches the specified selector.
3. **swag**: As mentioned earlier, this is not a standard JavaScript method and might be some proprietary or experimental implementation.

**Pros and Cons**

1. **getElementById**:
	* Pros: Simple, efficient, and widely supported by older browsers.
	* Cons: May return multiple elements if there are multiple elements with the same ID, which can lead to unexpected behavior.
2. **querySelector**:
	* Pros: Flexible, powerful, and allows for more complex selectors.
	* Cons: Might be slower than `getElementById` due to the overhead of parsing CSS selectors.
3. **swag**: Since it's not a standard method, its performance and behavior might vary depending on the implementation.

**Library/Utility Used**

None are explicitly mentioned in the provided code snippets, but I assume that `querySelector` uses the W3C Selectors API, which is a widely adopted standard for CSS selectors.

**Special JavaScript Feature/Syntax**

None of the methods use any special or experimental JavaScript features. They are all standard DOM manipulation techniques.

**Other Alternatives**

If you're interested in comparing other element retrieval methods, here are some alternatives:

1. **querySelectorAll**: Retrieves multiple elements that match the specified selector.
2. **getAttribute**: Retrieves the value of a specific attribute from an element (not suitable for retrieving elements by ID).
3. **getElementsByClassName** (older browsers): Retrieves multiple elements with a specific class name.

Keep in mind that these alternatives might have different performance characteristics, and their usage depends on the specific use case.

I hope this explanation helps you understand the benchmark and its various aspects!

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.114 Safari/537.36

Browser/OS: Chrome 89 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
getElementById	3139694.0 Ops/sec
querySelector	1229753.8 Ops/sec
swag	2094674.9 Ops/sec

Related benchmarks:

getElementById vs querySelector - multi level (version: 0)

Comparing performance of: getElementById vs querySelector vs swag

Created: 3 years ago by: Guest

Jump to the latest result

getElementById

querySelector

swag

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):