Benchmark: querySelector (NODE TO NODE) vs querySelectorAll

HTML Preparation code:

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Tests:

querySelector from one node to next
let node = document.querySelector('.test', element => { element.classList.add("read"); }); while(node) { node = node.querySelector('.test', element => { element.classList.add("read"); }); }
querySelectorAll
document.querySelectorAll(".test", elements => { elements.forEach(element => { element.classList.add("read") }) })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector from one node to next
querySelectorAll

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared, and the pros/cons of each approach.

**What is being tested?**

The benchmark compares the performance of two DOM query methods:

1. `querySelector`: which searches for an element by its CSS selector and returns the first matching element.
2. `querySelectorAll`: which searches for all elements that match a given CSS selector and returns a NodeList or HTMLCollection.

**Options compared:**

Two approaches are being compared:

1. **Sequential `querySelector`**: The benchmark uses `querySelector` in a sequential manner, where each call to `querySelector` is made on the previously selected element's child node.
2. **`querySelectorAll`**: The benchmark uses `querySelectorAll` to select all elements that match the CSS selector.

**Pros and cons of each approach:**

1. **Sequential `querySelector`**:
	* Pros:
		+ Can be more efficient for searching a single, specific element repeatedly.
		+ May use less memory since only one element is held in the DOM.
	* Cons:
		+ Requires multiple calls to `querySelector`, which can lead to additional overhead due to the DOM mutation and garbage collection.
2. **`querySelectorAll`**:
	* Pros:
		+ More efficient for searching multiple elements that match a specific CSS selector.
		+ Can be faster since it only requires a single call to `querySelector`.
	* Cons:
		+ May consume more memory since the entire NodeList or HTMLCollection is stored in the DOM.

**Library and its purpose:**

The benchmark uses the following libraries:

1. None explicitly mentioned, but `document.querySelector` and `document.querySelectorAll` are built-in DOM methods.
2. No third-party libraries are used.

**Special JS feature or syntax:**

None mentioned.

Now, let's consider alternative approaches:

* **Using `querySelector` with a callback function**: Instead of using the first argument to `querySelector`, you could use a callback function to manipulate the selected element. This might affect performance but can be useful for certain scenarios.
* **Using `getElementsByClassName` instead of `querySelectorAll`**: If you only need to select elements by class name, `getElementsByClassName` might be faster and more efficient than `querySelectorAll`.
* **Caching the result of `querySelectorAll`**: If you need to reuse the result of `querySelectorAll`, consider caching it in a variable to avoid re-executing the query.

Keep in mind that these alternatives are not specifically addressed by this benchmark, but they might be worth exploring in other scenarios.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Firefox/102.0

Browser/OS: Firefox 102 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
querySelector from one node to next	4160186.8 Ops/sec
querySelectorAll	2699830.5 Ops/sec

Related benchmarks:

querySelector (NODE TO NODE) vs querySelectorAll (version: 0)

Comparing performance of: querySelector from one node to next vs querySelectorAll

Created: 2 years ago by: Guest

Jump to the latest result

querySelector from one node to next

querySelectorAll

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):