Benchmark: querySelector vs getElementsByClassName with get

HTML Preparation code:

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

Tests:

querySelector
document.querySelector(".test")
getElementsByClassName
document.getElementsByClassName("test")
getElementsByClassName with get
document.getElementsByClassName("test")[0]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName
getElementsByClassName with get

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/111.0.0.0 Safari/537.36

Browser/OS: Chrome 111 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelector	596864.4 Ops/sec
getElementsByClassName	5719937.0 Ops/sec
getElementsByClassName with get	4704966.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data and explain what is tested, the options compared, pros and cons of each approach, and other considerations.

**Benchmark Definition**

The benchmark definition represents three different approaches to selecting elements in HTML documents:

1. `document.querySelector(".test")`: This approach uses the `querySelector` method to select an element with a CSS selector that matches the class "test".
2. `document.getElementsByClassName("test")`: This approach uses the `getElementsByClassName` method to retrieve all elements with the class "test" and returns them as an HTMLCollection.
3. `document.getElementsByClassName("test")[0]`: This is similar to the previous approach but returns only the first element from the resulting collection.

**Options Compared**

The three approaches are compared in terms of performance, specifically:

* `getElementsByClassName` with or without accessing the first element
* `querySelector`

**Pros and Cons of Each Approach**

1. **querySelector**
	* Pros:
		+ More concise and expressive syntax.
		+ Less overhead due to native implementation in modern browsers.
	* Cons:
		+ May not work as expected in older browsers or with non-standard CSS selectors.
2. **getElementsByClassName** without accessing the first element
	* Pros:
		+ Works consistently across all browsers, including older ones.
	* Cons:
		+ Returns an HTMLCollection, which can be slower and less efficient than native methods like `querySelector`.
3. **getElementsByClassName with get**
	* Pros:
		+ Similar performance to `querySelector` for most use cases (i.e., accessing the first element).
	* Cons:
		+ May not work as expected in older browsers or with non-standard CSS selectors.

**Library and Purpose**

None of the approaches rely on external libraries. However, `getElementsByClassName` is a native method in HTML5, which means it's built into the browser and doesn't require any additional dependencies.

**Special JS Feature or Syntax**

None of the benchmark definitions use special JavaScript features or syntax that would require specific explanations.

**Other Considerations**

When choosing between these approaches, consider the following factors:

* Browser support: If you need to support older browsers, `getElementsByClassName` without accessing the first element might be a safer choice.
* Performance: For most modern browser use cases, `querySelector` or `getElementsByClassName with get` will likely outperform the other approach.
* Code readability and conciseness: `querySelector` is often preferred for its concise syntax.

**Alternative Approaches**

Other alternatives to consider:

* Using `document.querySelectorAll(".test")`: This returns a NodeList (an array-like object) containing all elements that match the CSS selector. While it's not as efficient as `querySelector`, it can be useful in certain scenarios.
* Implementing custom element selectors: Some libraries or frameworks provide custom element selection methods, such as React's `useSelector` hook.

Keep in mind that these alternative approaches might have different performance characteristics and may require additional setup or dependencies.

Related benchmarks:

querySelector vs getElementsByClassName with get (version: 0)

Comparing performance of: querySelector vs getElementsByClassName vs getElementsByClassName with get

Created: one year ago by: Registered User

Jump to the latest result

querySelector

getElementsByClassName

getElementsByClassName with get

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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