Benchmark: document.body vs document.querySelector on element

HTML Preparation code:

<!DOCTYPE html>
<html lang="ru">
<head>
</head>
<body>
  <div id="foo"></div>
</body>
</html>

Tests:

querySelector
const pageBody = document.querySelector('#foo');
Direct access
const pageBody = document.body.querySelector('#foo');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
Direct access

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:139.0) Gecko/20100101 Firefox/139.0

Browser/OS: Firefox 139 on Windows

View result in a separate tab

Test name	Executions per second
querySelector	3333650.8 Ops/sec
Direct access	3185445.5 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

**Understanding the Benchmark**

The provided JSON represents a JavaScript microbenchmark test case on MeasureThat.net, which measures the performance of two different approaches to access an HTML element: `document.body` and `document.querySelector`. The benchmark is designed to compare the execution times of these two methods.

**Options Compared**

Two options are compared in this benchmark:

1. **Direct Access (Document Body)**: This approach uses the `document.body` property to directly access the `<body>` element of an HTML document.
2. **QuerySelector**: This approach uses the `document.querySelector()` method, which searches for an element by its CSS selector.

**Pros and Cons**

Here's a brief overview of each approach:

* **Direct Access (Document Body)**
	+ Pros: Simple and straightforward to use. No additional DOM elements or queries are needed.
	+ Cons: This approach requires the existence of the `<body>` element in the HTML document, which may not always be the case.
* **QuerySelector**
	+ Pros: More flexible and powerful than direct access. Can search for elements using CSS selectors, making it easier to target specific elements.
	+ Cons: May introduce additional overhead due to the DOM query mechanism.

**Library Used**

Neither of these approaches relies on a specific library. However, the `querySelector` method is an API provided by modern browsers and can be used without any external dependencies.

**Special JS Feature or Syntax**

There are no special JavaScript features or syntax used in this benchmark that would require knowledge beyond basic JavaScript programming.

**Other Considerations**

When considering performance optimizations or DOM manipulation, the choice between direct access and `querySelector` depends on the specific use case. If you need to frequently access a specific element within a document, using `querySelector` might be more efficient. However, if you're working with simple cases where direct access is sufficient, it may be faster.

**Alternatives**

Other alternatives for accessing DOM elements include:

1. **`getElementsByClassName()`**: Similar to `querySelector`, but uses class names instead of CSS selectors.
2. **`getElementById()`**: Accesses an element by its ID attribute.
3. **`getElementsByTagName()`**: Returns a collection of elements with the specified tag name.

These alternatives may have different performance characteristics and usage scenarios, depending on the specific requirements of your project.

Related benchmarks:

document.body vs document.querySelector on element (version: 0)

Comparing performance of: querySelector vs Direct access

Created: 4 years ago by: Guest

Jump to the latest result

querySelector

Direct access

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):