Benchmark: document.body vs document.querySelector('body') is performence2

HTML Preparation code:

<!doctype html>
<html><head></head>
  <body><h1 class="hello"></body>
</html>

Tests:

querySelector
const body = document.querySelector('body'); console.log(body);
document.body;
const body = document.body; console.log(body);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
document.body;

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser/OS: Chrome 123 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelector	128756.7 Ops/sec
document.body;	134575.9 Ops/sec

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

LLMs can make mistakes. Check important info.

Measuring performance and benchmarking are essential skills for any software engineer, and JavaScript is a particularly challenging language to optimize due to its dynamic nature and complex interactions.

Let's break down the provided JSON benchmark definition and test cases.

**What is being tested?**

The benchmark compares two approaches to access the `<body>` element in an HTML document: using `document.body` versus `document.querySelector('body')`. The goal is to determine which approach is faster and more efficient.

**Options compared:**

1. **Direct property access**: `const body = document.body;`
2. **QuerySelector API**: `const body = document.querySelector('body');`

**Pros and cons of each approach:**

* Direct property access:
	+ Pros:
		- Typically faster, as it involves a direct property lookup.
		- Easier to read and understand for simple cases.
	+ Cons:
		- May not work as expected in certain situations (e.g., if the `body` element has multiple names).
		- Can lead to brittle code if assumptions are made about the document structure.
* QuerySelector API:
	+ Pros:
		- More flexible and powerful, allowing for more complex queries.
		- Handles cases where elements have multiple names or attributes.
	+ Cons:
		- Typically slower than direct property access, due to the additional overhead of the query.
		- Can be more difficult to read and understand for simple cases.

**Other considerations:**

* The performance difference between these two approaches can vary depending on factors such as browser version, device platform, and operating system. In this benchmark, Chrome 123 on a desktop Mac OS X is used.
* Other libraries or frameworks may also impact the performance of these approaches. For example, if a library like jQuery is included in the test page, it could alter the results.

**Library usage:**

In this benchmark, no additional libraries are used. However, if a library like jQuery were to be included, it would likely have its own way of accessing the `body` element, such as using `$().html()` or `$().attr('body')`. This could potentially impact the performance and results of the benchmark.

**Special JS features:**

None are mentioned in this benchmark definition. However, if a special feature like `const` or `let` were used, it would indicate how the variables are declared and scoped within the test cases.

In summary, this benchmark compares two common approaches to access the `<body>` element in an HTML document: direct property access versus the QuerySelector API. While direct property access is typically faster, the QuerySelector API offers more flexibility but at a potential performance cost. The results of this benchmark can provide insights into the trade-offs between these approaches and help optimize code for specific use cases.

As for alternatives to this benchmark, some possible scenarios include:

* Comparing multiple query methods (e.g., `document.querySelector`, `document.getElementById`, `querySelectorAll`)
* Examining the performance impact of different HTML structures or document manipulations
* Investigating the effects of caching or memoization on these benchmarks
* Using a more comprehensive testing framework to identify potential bottlenecks in code
* Implementing a profiling tool to analyze performance issues and provide insights into resource allocation.

Related benchmarks:

document.body vs document.querySelector('body') is performence2 (version: 0)

Comparing performance of: querySelector vs document.body;

Created: 3 years ago by: Guest

Jump to the latest result

querySelector

document.body;

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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