Benchmark: querySelector() vs getElementsByClassName()[0] vs getElementById()

HTML Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName
getElementById()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36

Browser/OS: Chrome 69 on Mac OS X 10.12.6

View result in a separate tab

Test name	Executions per second
querySelector	1594499.4 Ops/sec
getElementsByClassName	1240211.2 Ops/sec
getElementById()	1969623.4 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its individual test cases.

**Benchmark Definition**

The benchmark is designed to compare the speed of three different approaches for selecting a single element from an HTML document:

1. `querySelector()`
2. `getElementsByClassName()[0]`
3. `getElementById()``

These methods are used to retrieve an element by its identifier, class name, or ID respectively.

**Library and Purpose**

The benchmark uses the following libraries:

* None explicitly mentioned in the provided JSON, but it's likely that the standard DOM API is being used.
* No additional libraries are required for this benchmark as it only involves basic HTML manipulation and JavaScript execution.

**Options Compared**

The three options compared are:

1. **`querySelector()`**: A method to select an element by its CSS selector syntax.
	* Pros: Fast, efficient, and flexible. It allows selecting multiple elements based on a single string.
	* Cons: May not work as expected if the HTML structure is complex or if the selector is ambiguous.
2. **`getElementsByClassName()`**: A method to retrieve all elements with a specific class name.
	* Pros: Allows retrieving multiple elements based on a single class, which can be useful in certain scenarios.
	* Cons: Returns an array of all matching elements, which can lead to slower performance if many elements match the class.
3. **`getElementById()`**: A method to retrieve an element by its ID attribute.
	* Pros: Fast and efficient for retrieving a single element with a unique ID.
	* Cons: May not work as expected if multiple elements have the same ID (which is not recommended in practice).

**Special JS Features**

The benchmark does not use any special JavaScript features or syntax. It only involves standard JavaScript execution and DOM manipulation.

**Alternatives**

Other alternatives for selecting an element from HTML include:

1. `getElementsByTagName()`: Retrieves all elements of a specific type (e.g., `document.getElementsByTagName('div')`).
2. `querySelectorAll()`: Similar to `querySelector()`, but returns all matching elements instead of a single one.
3. Using jQuery or other libraries that provide more advanced DOM manipulation capabilities.

Keep in mind that the choice of method depends on the specific use case and requirements.

Related benchmarks:

querySelector() vs getElementsByClassName()[0] vs getElementById() (version: 0)

Testing query speed of a single element

Comparing performance of: querySelector vs getElementsByClassName vs getElementById()

Created: 6 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

getElementById()

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):