Benchmark: document.querySelectorAll vs document.body.querySelectorAll

HTML Preparation code:

<div class="test"></div>

Tests:

querySelectorAll
document.querySelectorAll(".test")
getElementsByClassName
document.body.querySelectorAll(".test")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelectorAll
getElementsByClassName

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.119 Safari/537.36

Browser/OS: Chrome 83 on Linux

View result in a separate tab

Test name	Executions per second
querySelectorAll	1252036.1 Ops/sec
getElementsByClassName	1428754.2 Ops/sec

Autogenerated LLM Summary (model llama3.1:latest, generated 2 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the details of this benchmark.

**Benchmark Description**

The benchmark compares two different ways to select HTML elements on a webpage:

1. `document.querySelectorAll` (short for querySelectorAll) - a method that returns all elements matching a specified CSS selector, in this case `.test`.
2. `document.body.querySelectorAll` - an alternative approach that selects the body element first and then uses its own `querySelectorAll` method to select elements with class `.test`.

**What is being tested?**

In this benchmark, we're measuring how quickly each of these two approaches can execute on a webpage.

**Test Case Options**

The test cases compare the execution speed of:

1. **`document.querySelectorAll(".test")`**: This method selects all elements with the class `".test"` directly from the document.
2. **`document.body.querySelectorAll(".test")`**: This approach first gets the body element using `document.body`, and then uses its own `querySelectorAll` method to select elements with class `".test"`. It's essentially a nested call, where we're querying the body element first.

**Pros/Cons of Different Approaches**

Here are some considerations for each approach:

1. **`document.querySelectorAll(".test")`**: Pros:
	* Direct and efficient way to select elements.
	* Avoids unnecessary nesting (i.e., calling `querySelectorAll` on the body element).
	* Generally faster, as shown in the benchmark results.

Cons:
	* May not be suitable if you need to operate on a specific scope (e.g., only selecting elements within the body or a specific container).

2. **`document.body.querySelectorAll(".test")`**: Pros:
	* Allows for more targeted selection within the scope of the body element.
	* Can be useful when working with complex HTML structures.

Cons:
	* May introduce additional overhead due to the nested call.

**Library and Special JS Features**

In this benchmark, there is no specific library or feature used. The code relies on standard JavaScript methods (`document.querySelectorAll` and `document.body.querySelectorAll`) available in most modern browsers.

**Other Alternatives**

For selecting elements on a webpage, you can also use:

1. **`getElementsByClassName`**: This method returns an HTMLCollection of elements with the specified class name.
2. **CSS Selectors**: You can use CSS selectors directly within your JavaScript code to select elements (e.g., `document.querySelector(".test")` or `document.querySelectorAll(".test")`).
3. **Other DOM methods**: Depending on your specific use case, you might find other DOM methods more suitable for selecting elements.

Overall, the benchmark demonstrates a simple and efficient approach using `document.querySelectorAll`. However, it's essential to consider the context of your project when choosing between different selection methods.

Related benchmarks:

document.querySelectorAll vs document.body.querySelectorAll (version: 0)

Comparing performance of: querySelectorAll vs getElementsByClassName

Created: 6 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByClassName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated 2 months ago):