Benchmark: Direct querySelector scope vs no scope

HTML Preparation code:

<div id='parent'>
  <div class="foo">
    <div class="bar">
      <div class="baz">
      </div>
    </div>
  </div>
</div>

Tests:

querySelector scope
document.getElementById("parent").querySelector(':scope > .foo')
querySelector no scope
document.getElementById("parent").querySelector('.foo')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector scope
querySelector no scope

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36

Browser/OS: Chrome 134 on Windows

View result in a separate tab

Test name	Executions per second
querySelector scope	2153084.8 Ops/sec
querySelector no scope	3189146.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, the options compared, pros and cons of those approaches, and other considerations.

**Benchmark Overview**

The provided benchmark tests two different approaches for selecting elements in HTML using `querySelector`. The test consists of:

1. A parent element (`<div id="parent">`) containing multiple child elements (`<div class="foo">`, `<div class="bar">`, and `<div class="baz">`).
2. Two individual test cases:
	* `querySelector scope`: Selects the `.foo` element inside the current scope of the query (i.e., the same scope as the parent element).
	* `querySelector no scope`: Does not consider the current scope, resulting in a slower performance.

**Options Compared**

The two options being compared are:

1. **Selector scope**: The query selector engine uses the element's scope to optimize the lookup process. In this case, it looks for elements inside the parent element.
2. **No scope**: The query selector engine does not consider the current scope, resulting in a slower performance.

**Pros and Cons**

* **Selector scope (with scope)**:
	+ Pros: Faster performance since the engine can optimize the lookup process using the element's scope.
	+ Cons: May not work as expected if the DOM is modified dynamically or if the `:scope` pseudo-class is not supported in certain browsers.
* **No scope**:
	+ Pros: Works consistently even when the DOM is modified dynamically, but may incur a performance penalty due to slower lookup.
	+ Cons: Less optimized performance compared to using the selector scope.

**Library and Purpose**

There is no library being used in this benchmark. However, it's worth noting that `querySelector` is a standard querySelector API function provided by modern browsers.

**Special JS Feature/Syntax**

None of the test cases use special JavaScript features or syntax beyond the standard HTML5 DOM APIs.

Related benchmarks:

Direct querySelector scope vs no scope (version: 0)

Comparing performance of: querySelector scope vs querySelector no scope

Created: 2 years ago by: Guest

Jump to the latest result

querySelector scope

querySelector no scope

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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