Benchmark: dataAttribute vs attribute vs Class Selector vs ID Selector

HTML Preparation code:

<div class="hello" id="hello" data-hello>Hello</div>

Tests:

Class
document.querySelector('.hello');
ID
document.querySelector('#hello');
data attribute
document.querySelector('[data-hello]');
just random attribute
document.querySelector('[class]');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Class
ID
data attribute
just random attribute

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Class	8431688.0 Ops/sec
ID	6196786.0 Ops/sec
data attribute	5894888.0 Ops/sec
just random attribute	5957003.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 5 months ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON compares different methods of selecting elements in the DOM using JavaScript's `document.querySelector()` method. Specifically, it tests four different selector types to measure their performance in terms of how many times per second they can be executed (Executions Per Second):

1. **Class Selector (`.hello`)**: This selector targets elements based on their class name. In this case, it selects the element with the class "hello".

2. **ID Selector (`#hello`)**: This selector targets elements based on their unique ID. Here, it selects the element with the ID "hello".

3. **Data Attribute Selector (`[data-hello]`)**: This selector targets elements that have a specific data attribute. In this case, it selects the element with the `data-hello` attribute.

4. **Just Random Attribute Selector (`[class]`)**: This general selector targets any element that has a `class` attribute, regardless of its value.

### Pros and Cons of Each Selector

1. **Class Selector (`.hello`)**:
   - **Pros**: 
     - Efficient if selecting multiple elements with the same class; performance remains high when there are many elements sharing the class.
   - **Cons**: 
     - Slightly slower than ID selectors since it can match multiple elements (though it’s highly optimized in modern browsers).
   
2. **ID Selector (`#hello`)**:
   - **Pros**: 
     - Fastest among the selectors tested. IDs are required to be unique within the HTML document, so the browser can quickly pinpoint the element.
   - **Cons**: 
     - Limited to selecting a single element since IDs are unique.
   
3. **Data Attribute Selector (`[data-hello]`)**:
   - **Pros**: 
     - Flexible as it allows for semantic HTML and custom attributes. Useful for applications where attributes are dynamically added.
   - **Cons**: 
     - Slowest among the test cases. The performance may degrade as more custom data attributes are used within the document.
   
4. **Just Random Attribute Selector (`[class]`)**:
   - **Pros**: 
     - Can select any element with a `class` attribute, making it helpful for more general queries.
   - **Cons**: 
     - The performance is generally slower than class and ID selectors since it is less specific and requires more work from the browser to match elements.

### Benchmark Results Analysis
Based on the latest benchmark results:
- The **Class Selector** (`.hello`) achieved the highest execution speed (approximately 8.43 million executions per second), suggesting that it remains highly optimized in modern browsers.
- The **ID Selector** (`#hello`) came in second (around 6.19 million), demonstrating its efficiency due to uniqueness.
- Both the **Data Attribute Selector** and the **Random Attribute Selector** performed similarly (around 5.89 million and 5.96 million executions per second, respectively), with the data attribute selector being slightly slower.

### Considerations
While performance is an important factor, it’s also crucial to consider readability and maintainability. Choosing an appropriate selector depends on the context:
- For unique elements, prefer ID selectors.
- For multiple elements with shared styles or behavior, class selectors are suitable.
- Data attributes enhance semantic HTML usage but at the cost of performance.

### Alternatives
Other methods for selecting DOM elements include:
- **Get Elements By Class Name**: `document.getElementsByClassName('hello')` can return a live HTMLCollection of elements which might be faster for certain scenarios.
- **Get Elements By Tag Name**: Uses `document.getElementsByTagName('div')`, but is less specific.
- **Get Element By Id**: `document.getElementById('hello')` for fetching a single element directly.

These alternatives may have their use cases but often involve trade-offs in terms of performance or specificity compared to `querySelector`. When choosing a method, developers should balance performance with the readability of their code and the specific requirements of their application.

Related benchmarks:

dataAttribute vs attribute vs Class Selector vs ID Selector (version: 1)

Comparing performance of: Class vs ID vs data attribute vs just random attribute

Created: 5 months ago by: Guest

Jump to the latest result

Class

ID

data attribute

just random attribute

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 5 months ago):