Benchmark: querySelector vs getElementsByClassName.0

HTML Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName[0]

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:87.0) Gecko/20100101 Firefox/87.0

Browser/OS: Firefox 87 on Linux

View result in a separate tab

Test name	Executions per second
querySelector	3623043.2 Ops/sec
getElementsByClassName[0]	6000114.0 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 test case and explain what is being tested, compared, and the pros and cons of each approach.

**What is being tested?**

The test case compares two methods to select an HTML element with a specific class: `document.querySelector(".test")` (also known as CSS selector) and `document.getElementsByClassName("test")[0]` (also known as traditional DOM-based method).

**Options compared**

Two options are being compared:

1. **CSS selector (`document.querySelector(".test")`)**: This method uses the CSS selector syntax to select an element based on its class.
2. **Traditional DOM-based method (`document.getElementsByClassName("test")[0]`)**: This method uses the `getElementsByClassName()` method to retrieve all elements with the specified class and then returns the first one.

**Pros and Cons of each approach**

**CSS Selector (QuerySelector)**

Pros:

* More concise and readable code
* Faster performance, especially for larger documents
* Can be used with multiple classes
* Allows for more complex selectors

Cons:

* Requires a compatible browser that supports CSS selectors
* May not work in older browsers or those with strict HTML parsing

**Traditional DOM-based Method (GetElementsByClassName)**

Pros:

* Works in all browsers, even older ones
* Easy to understand and implement
* No dependencies on CSS selectors

Cons:

* More verbose code
* Can be slower for larger documents due to the need to retrieve all matching elements
* Limited flexibility in selecting elements

**Library and its purpose**

In this test case, no specific library is mentioned. However, if we consider popular JavaScript libraries that provide DOM manipulation functionality, some examples include:

* jQuery: A widely used library that provides an alternative syntax for DOM manipulation, including a `querySelectorAll()` method.
* Zepto: A lightweight alternative to jQuery that also provides a `querySelectorAll()` method.

**Special JS feature or syntax**

This test case does not mention any special JavaScript features or syntax. It only uses standard JavaScript and CSS selectors.

**Other alternatives**

If you're looking for alternative methods to select HTML elements, consider:

* `getElementById()`: Selects an element by its ID.
* `getElementsByTagName()`: Returns a collection of all elements with a specific tag name.
* `getElementsByAttribute()`: Returns all elements that have a specific attribute.

Keep in mind that these alternatives may not be as efficient or flexible as the CSS selector method used in this test case.

Related benchmarks:

querySelector vs getElementsByClassName.0 (version: 0)

Comparing performance of: querySelector vs getElementsByClassName[0]

Created: 4 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName[0]

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):