Benchmark: querySelector(nth) vs querySelectorAll

HTML Preparation code:

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

Tests:

document.querySelector(nth)
document.querySelector("[class*=test]:nth-child(9)")
document.querySelectorAll
document.querySelectorAll('.test')[9]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
document.querySelector(nth)
document.querySelectorAll

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
document.querySelector(nth)	2739883.8 Ops/sec
document.querySelectorAll	4902956.5 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmark, hosted on MeasureThat.net. The benchmark compares the performance of two approaches: `querySelectorAll` and `querySelector`. Both methods are used to select elements with a specific class name (`test`) using CSS selectors.

**Options Compared**

Two options are compared:

1. **`document.querySelector(nth)`**: This method uses the `:nth-child` pseudo-class to select an element based on its position within its sibling nodes.
2. **`document.querySelectorAll('.test')[9]`**: This method uses the `querySelectorAll` method with a CSS selector (`.` followed by the class name) and then indexes into the resulting NodeList to retrieve the 10th element.

**Pros and Cons of Each Approach**

1. **`document.querySelector(nth)`**:
	* Pros: Can be more efficient when selecting elements based on their position within the DOM.
	* Cons: May not work correctly in older browsers or when working with large datasets, as it relies on the `:nth-child` pseudo-class.
2. **`document.querySelectorAll('.test')[9]`**:
	* Pros: Works in all modern browsers and can be more efficient for larger datasets, as it returns a NodeList that can be indexed directly.
	* Cons: May require more memory to store the result, especially for large datasets.

**Library Used**

None of the provided benchmark code uses any external libraries. However, it's worth noting that `querySelectorAll` is part of the DOM API, which is a built-in feature in modern browsers.

**Special JS Features/Syntax**

The benchmark uses the `:nth-child` pseudo-class, which is a CSS selector syntax. This allows you to select elements based on their position within their sibling nodes. The `(Macintosh; Intel Mac OS X 10_15_7)` part of the User Agent String appears to be a test device identifier.

**Other Alternatives**

For this specific benchmark, there are no other alternatives being compared. However, if you wanted to compare other approaches, some possible options could include:

* Using `querySelector` with a different CSS selector
* Using a library like jQuery to simplify the selection process
* Using a virtual DOM library to render elements and measure performance

Keep in mind that this benchmark is focused on comparing two specific methods within the DOM API.

Related benchmarks:

querySelector(nth) vs querySelectorAll (version: 0)

Comparing performance of: document.querySelector(nth) vs document.querySelectorAll

Created: 2 years ago by: Guest

Jump to the latest result

document.querySelector(nth)

document.querySelectorAll

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):