Benchmark: querySelector vs getElementsByClassName vs attributes

HTML Preparation code:

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

Tests:

querySelector
document.querySelector(".test")
getElementsByClassName
document.getElementsByClassName(".test")
querySelectorAll
document.querySelectorAll('.test')
querySelector (attribute)
document.querySelector('[class="test"]')
querySelectorAll (attribute)
document.querySelectorAll('[class="test"]')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName
querySelectorAll
querySelector (attribute)
querySelectorAll (attribute)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.54 Safari/537.36

Browser/OS: Chrome 94 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelector	4016229.5 Ops/sec
getElementsByClassName	4973939.0 Ops/sec
querySelectorAll	1803766.0 Ops/sec
querySelector (attribute)	2139793.8 Ops/sec
querySelectorAll (attribute)	1041918.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided benchmark measures the performance difference between three DOM query methods in JavaScript: `querySelector`, `getElementsByClassName`, and their attribute-based variants, `querySelector` and `querySelectorAll`. The test creates a simple HTML element (`<div class="test"></div>`) and uses each method to retrieve it.

**Methods Compared**

1. **`document.querySelector('.test')`**: Uses the `querySelector` method with a class selector.
2. **`document.getElementsByClassName('test')`**: Uses the `getElementsByClassName` method with a class selector.
3. **`document.querySelectorAll('.test')`**: Uses the `querySelectorAll` method with a class selector.
4. **`document.querySelector('[class="test"]')`**: Uses the `querySelector` method with an attribute-based selector (using square brackets instead of dots).
5. **`document.querySelectorAll('[class="test"]')`**: Uses the `querySelectorAll` method with an attribute-based selector.

**Pros and Cons of Each Approach**

1. **`document.querySelector('.test')`**
	* Pros: Fast, widely supported, and efficient for most use cases.
	* Cons: May not work correctly if there are multiple elements with the same class name (can lead to inconsistent results).
2. **`document.getElementsByClassName('test')`**
	* Pros: Works even if there are multiple elements with the same class name, but may be slower due to its more complex implementation.
	* Cons: Less efficient than `querySelector`, can be slower for large datasets.
3. **`document.querySelectorAll('.test')`**
	* Pros: More flexible and efficient than `getElementsByClassName`, returns a NodeList (which is an array-like object) containing all matching elements.
	* Cons: May return more elements than expected if there are duplicate class names or nested selectors.
4. **`document.querySelector('[class="test"]')`** and **`document.querySelectorAll('[class="test"]')`**
	* Pros: Allows for more flexible attribute-based selectors, can be faster than using class selectors for specific attributes.
	* Cons: Less widely supported, may require additional parsing steps.

**Library Usage**

In this benchmark, no libraries are used. However, it's worth noting that some modern browsers support the `DOMTokenList` API, which provides a more efficient and flexible way to work with class names and attribute selectors.

**Special JS Features or Syntax**

None mentioned in this specific benchmark.

Related benchmarks:

querySelector vs getElementsByClassName vs attributes (version: 0)

Comparing performance of: querySelector vs getElementsByClassName vs querySelectorAll vs querySelector (attribute) vs querySelectorAll (attribute)

Created: 3 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

querySelectorAll

querySelector (attribute)

querySelectorAll (attribute)

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):