Benchmark: querySelector vs getElementByTagName

HTML Preparation code:

<div><span></span></div>

Tests:

querySelector
document.querySelector('span')
getElementByTagName
document.getElementsByTagName('span')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementByTagName

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**What is tested?**

The provided JSON benchmark tests two different methods to retrieve an element from a HTML document: `document.querySelector` and `document.getElementsByTagName`. The benchmarks aim to compare the performance of these two approaches.

**Options being compared**

*   **querySelector**: A method introduced in ECMAScript 5 (2009) that allows selecting elements using CSS selectors.
*   **getElementsByTagName**: A traditional method that returns a collection of all elements with the specified tag name.

**Pros and Cons of each approach:**

### QuerySelector

Pros:

1.  **Flexibility**: Allows selecting elements based on their class, id, attributes, or CSS properties, making it more versatile than `getElementsByTagName`.
2.  **Readability**: Can be more readable when writing code since it's often easier to understand the intent behind a CSS selector.
3.  **Performance**: Generally faster than `getElementsByTagName`, as it uses a single DOM query that can return multiple results.

Cons:

1.  **Browser Support**: Not supported in older browsers (pre-ECMAScript 5).
2.  **Complexity**: Can be more challenging to maintain, especially for complex selectors or scenarios where the element may not exist.

### GetElementsByTagName

Pros:

1.  **Browser Support**: Works across all major browsers and versions.
2.  **Simple**: Easy to implement and understand, as it's a straightforward method that returns an array of elements with the specified tag name.

Cons:

1.  **Performance**: Typically slower than `querySelector`, especially when dealing with large datasets or complex queries.

**Library usage**

None of the provided benchmarks use any external libraries for their test cases.

**Special JS features or syntax**

There's no special JavaScript feature or syntax used in these benchmark definitions, as they only focus on comparing the performance of basic DOM query methods (`querySelector` and `getElementsByTagName`).

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.127 Safari/537.36

Browser/OS: Chrome 100 on Windows

View result in a separate tab

Test name	Executions per second
querySelector	4403566.0 Ops/sec
getElementByTagName	5195825.5 Ops/sec

Related benchmarks:

querySelector vs getElementByTagName (version: 0)

Comparing performance of: querySelector vs getElementByTagName

Created: 2 years ago by: Guest

Jump to the latest result

querySelector

getElementByTagName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):