Benchmark: querySelector vs classList.contains

HTML Preparation code:

<div></div>

Tests:

1
document.querySelector("div")
2
const div = document.querySelector("div"); div.classList.contains("test")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
1
2

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 months ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.3 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 18 on iOS 18.3.1

View result in a separate tab

Test name	Executions per second
1	7779280.5 Ops/sec
2	6539062.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what is being tested.

**Benchmark Definition**

The benchmark definition specifies two test cases:

1. `document.querySelector("div")`: This test case uses the `querySelector` method to select an element with the tag name "div". The purpose of this test is likely to measure the performance of the browser's DOM query engine.
2. `const div = document.querySelector("div"); div.classList.contains("test")`: This test case is similar to the first one, but it also checks if the selected element has a class attribute called "test" using the `classList.contains` method.

**Options Compared**

The two options being compared are:

1. `document.querySelector("div")`: This method uses an XPath-like syntax to select elements.
2. Using the `querySelectorAll` method and then iterating over the results to check if the first element has a class attribute called "test".

**Pros and Cons of Each Approach**

1. **`document.querySelector("div")`**:
	* Pros: Simple and straightforward, no need to create an iterator or iterate over the results.
	* Cons: May not be as efficient as other methods, especially for larger datasets.
2. **Using `querySelectorAll` and then checking the first element**:
	* Pros: Can be more efficient than using `querySelector`, especially if you need to check multiple elements. However, it requires creating an iterator or iterating over the results, which can add overhead.
	* Cons: May require more memory and processing power, especially for large datasets.

**Library and Purpose**

In both test cases, the `document` object is used, which is a built-in library in JavaScript. The `document` object provides access to the Document Object Model (DOM), which represents the structure of an HTML document.

**Special JS Feature or Syntax**

There are no special JS features or syntax mentioned in this benchmark.

**Other Alternatives**

If you want to test alternative methods for selecting elements, here are a few options:

1. Using `getElementById` instead of `querySelector`: This method selects an element by its ID attribute.
2. Using `getElementsByClassName` instead of `querySelectorAll`: This method returns a NodeList of all elements with the specified class name.
3. Using a CSS selector engine like jQuery's `.selector()` function: This can provide more powerful and flexible selection capabilities, but may also introduce overhead.

**Additional Considerations**

When writing benchmarks, it's essential to consider factors such as:

1. **Cache and recompile**: Ensure that your benchmark is not affected by caching or recompilation of the JavaScript code.
2. **Input data**: Use a representative input dataset to ensure accurate results.
3. **Browser variability**: Test on multiple browsers to account for differences in rendering, layout, and performance.

By considering these factors, you can write more robust and reliable benchmarks that accurately measure the performance of your codebase.

Related benchmarks:

querySelector vs classList.contains (version: 0)

Comparing performance of: 1 vs 2

Created: one year ago by: Guest

Jump to the latest result

1

2

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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