Benchmark: getElementById vs querySelector data-id2

HTML Preparation code:

<div id="testElement"></div>
<div data-id="testElement"></div>

Tests:

getElementById
var el = document.getElementById('testElement'); var className = el.className;
querySelector
var el = document.querySelector('[data-id=testElement]'); var className = el.className;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
querySelector

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 on MeasureThat.net.

The provided benchmark tests two ways to retrieve an element by its `id` and then get its `className`. The options being compared are:

1. **`document.getElementById('testElement')`**: This is a traditional way of retrieving an element using its `id` attribute. The method returns the first matching element in the DOM, or `null` if no match is found.
2. **`document.querySelector('[data-id=testElement]')`**: This method uses CSS selectors to retrieve elements based on their attributes and classes. In this case, it's searching for an element with a `data-id` attribute equal to `"testElement"`.

**Pros and Cons:**

* **`document.getElementById('testElement')`**:
	+ Pros: Wide support across browsers, simple syntax, and fast execution.
	+ Cons: Can be slower than CSS selectors, especially if the DOM is complex or contains many elements with similar `id` values.
* **`document.querySelector('[data-id=testElement]')`**:
	+ Pros: More flexible and efficient than traditional `id`-based retrieval, as it can also retrieve elements based on class names, attributes, and other CSS selectors. However, its performance might be slower due to the additional complexity of CSS selector evaluation.
	+ Cons: Requires the use of a custom attribute (`data-id`) and might have varying levels of browser support.

**Library usage:** None in this benchmark.

**Special JS features/syntax:** The `data-` prefix is used in the HTML attribute, which is a modern feature that allows developers to attach custom data attributes to elements. This is not specific to JavaScript but rather an HTML feature.

Now, let's discuss some alternatives:

* **Using `document.querySelector('#testElement')` instead of `document.getElementById('testElement')`:** Although this method uses the same CSS selector syntax as the second test case, it would retrieve the first matching element in the DOM by its `id`, rather than using a custom attribute.
* **Using other CSS selectors:** You could experiment with different CSS selectors, such as `[class^='test']` or `[data-attribute='custom-value']`, to see how they impact performance.

Keep in mind that this benchmark specifically compares two traditional methods and the more modern `querySelector` method. If you want to explore alternative approaches, feel free to create a new benchmark on MeasureThat.net!

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36

Browser/OS: Chrome 85 on Mac OS X 10.15.6

View result in a separate tab

Test name	Executions per second
getElementById	3616977.8 Ops/sec
querySelector	1675157.6 Ops/sec

Related benchmarks:

getElementById vs querySelector data-id2 (version: 0)

Comparing performance of: getElementById vs querySelector

Created: 4 years ago by: Guest

Jump to the latest result

getElementById

querySelector

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):