Benchmark: querySelector vs querySelectorAll simple (single element result)

HTML Preparation code:

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

querySelector
document.querySelector(".test")
querySelectorAll
document.querySelectorAll(".test")[0]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
querySelectorAll

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark and explain what's being tested, compared, and their pros and cons.

**Benchmark Definition**

The benchmark is designed to compare two approaches: `document.querySelector` and `document.querySelectorAll`. The goal is to measure which approach performs better in a simple scenario where only one element with the class "test" is expected to be present.

**Options Compared**

Two options are compared:

1. **`document.querySelector('.test')`**: This method selects the first element that matches the specified CSS selector.
2. **`document.querySelectorAll('.test')[0]`**: This method returns an array of elements that match the specified CSS selector, and then extracts the first element from the array.

**Pros and Cons**

1. **`document.querySelector('.test')`**:
	* Pros:
		+ More efficient when only one element is expected to be present.
		+ Returns a single value (the matched element), which can be useful for further processing.
	* Cons:
		+ May throw an error if no matching elements are found.
		+ Not suitable for scenarios where multiple elements match the selector, as it will return all of them.
2. **`document.querySelectorAll('.test')[0]`**:
	* Pros:
		+ Returns a single element even if multiple elements match the selector (by taking the first one).
		+ Suitable for scenarios where only one element is expected to be present or when the index doesn't matter.
	* Cons:
		+ Less efficient than `querySelector` since it involves searching through all matching elements and extracting the first one.

**Library and Special JS Feature**

There are no specific libraries used in this benchmark. However, JavaScript engines like Firefox support some features that might be relevant to this benchmark:

1. **Array indexing**: Both tests use array indexing (`[0]`) to extract a single element from an array.
2. **CSS selector engine**: The browser's CSS selector engine is used for both `querySelector` and `querySelectorAll`.

**Other Alternatives**

If you wanted to write similar benchmarks, you could compare other methods:

1. **`document.querySelectorAll('.test')`**: Similar to `querySelectorAll`, but returns all matching elements in an array.
2. **`document.getElementsByClassName('test')[0]`**: Compares the performance of using `getElementsByClassName` instead of CSS selectors.
3. **`element.matchedCount`**: Measures the performance of using the `matchedCount` property on the element (if supported).

To create a similar benchmark, you would need to:

1. Write a script that creates multiple elements with the class "test".
2. Create two test cases: one for `querySelector` and one for `querySelectorAll`.
3. Use a tool like MeasureThat.net or write your own benchmarking framework to measure the execution time of each test case.

Keep in mind that benchmarking can be complex, and results may vary depending on the specific JavaScript engine, browser, and hardware used.

Related benchmarks:

querySelector vs querySelectorAll simple (single element result) (version: 0)

Comparing performance of: querySelector vs querySelectorAll

Created: 3 years ago by: Guest

Jump to the latest result

querySelector

querySelectorAll

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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