Benchmark: querySelector vs getElementsByClassName _2 (Get first element)

HTML Preparation code:

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Tests:

querySelector
document.querySelector(".test")
getElementsByClassName
document.getElementsByClassName(".test")[0]
getElementsByClassName (item)
document.getElementsByClassName(".test").item(0);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName
getElementsByClassName (item)

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.113 Safari/537.36

Browser/OS: Chrome 81 on Windows 7

View result in a separate tab

Test name	Executions per second
querySelector	2511589.0 Ops/sec
getElementsByClassName	2012786.1 Ops/sec
getElementsByClassName (item)	2496218.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark JSON and explain what is being tested, compared, and their pros and cons.

**Benchmark Definition**

The benchmark defines two main test cases:

1. `document.querySelector(".test")`
2. `document.getElementsByClassName(".test")[0]`
3. `document.getElementsByClassName(".test").item(0);`

All three test cases are designed to retrieve the first element with the class "test" from an HTML document.

**Script Preparation Code**

The script preparation code is empty, which means that the benchmark assumes the test HTML document is provided as part of the `Html Preparation Code`.

**Html Preparation Code**

The `Html Preparation Code` contains a repeated sequence of five `<div>` elements with the class "test", ensuring that there are enough elements for the querySelector and getElementsByClassName functions to operate on.

**What's being tested?**

* **QuerySelector**: The `document.querySelector(".test")` function is being tested, which returns the first element matching the specified CSS selector. In this case, it will return one of the five `<div>` elements with the class "test".
* **getElementsByClassName**: The `document.getElementsByClassName(".test")[0]` function is being tested, which returns an array of all elements with the specified class name. In this case, it will return an array containing all five `<div>` elements with the class "test".
* **getElementsByClassName (item)**: The `document.getElementsByClassName(".test").item(0)` function is being tested, which returns the first element in the resulting array from getElementsByClassName. In this case, it will return one of the five `<div>` elements with the class "test".

**Options compared**

The benchmark compares three different approaches:

* **QuerySelector**: Returns the first matching element
	+ Pros: Simple and efficient, suitable for most use cases.
	+ Cons: May not be as flexible or powerful as other methods (e.g., getElementsByClassName).
* **getElementsByClassName**: Returns an array of all matching elements
	+ Pros: More flexible and powerful than QuerySelector, can handle multiple matches.
	+ Cons: Returns an array, which may require additional processing to extract the first element.
* **getElementsByClassName (item)**: Returns the first element in the resulting array from getElementsByClassName
	+ Pros: Convenient way to get the first matching element without having to process the entire array.
	+ Cons: May be slower than QuerySelector for most use cases.

**Library**

There is no explicit library mentioned in the benchmark definition. However, it's worth noting that both `querySelector` and `getElementsByClassName` are part of the W3C DOM API, which is a standardized set of APIs for manipulating HTML documents.

**Special JS feature or syntax**

None of the test cases utilize any special JavaScript features or syntax beyond what is standard in modern JavaScript.

Related benchmarks:

querySelector vs getElementsByClassName _2 (Get first element) (version: 0)

Comparing performance of: querySelector vs getElementsByClassName vs getElementsByClassName (item)

Created: 4 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

getElementsByClassName (item)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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