Benchmark: getElementById vs querySelectorrthtyj

HTML Preparation code:

<div class="testElement"></div>

Tests:

getElementById
var el = document.getElementsByClassName('testElement')[0]; var className = el.className;
querySelector
var el = document.querySelector('.testElement'); var className = el.className;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
querySelector

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark compares two approaches to retrieve an element from HTML by its class name: `getElementsByClassName` (identified as `getElementById`) and `querySelector`. These methods are part of the DOM (Document Object Model) API in JavaScript, which allows web developers to interact with the structure and content of web pages.

**Test Case 1: getElementById**

In this test case, the script retrieves an element from HTML using `getElementsByClassName` and assigns it to a variable `el`. The code then extracts the value of the `className` property from the `el` object. This method has been widely used in web development for retrieving elements by class names.

**Test Case 2: querySelector**

In this test case, the script retrieves an element from HTML using `querySelector` and assigns it to a variable `el`. The code then extracts the value of the `className` property from the `el` object. This method is more modern and efficient than `getElementsByClassName`, as it allows for more flexible and expressive selectors.

**Comparison of Options**

The two options being compared are:

* `getElementsByClassName`: An older, more verbose approach that returns a collection of elements matching the specified class name.
* `querySelector`: A newer, more concise approach that allows for more flexible and expressive selectors.

**Pros and Cons of Each Approach**

**getElementsByClassName:**

Pros:

* Widely supported by older browsers
* Can be used with multiple classes

Cons:

* Returns a collection of elements (arrays), which can lead to slower performance in some cases
* Less readable code, as it requires more verbose syntax

**querySelector:**

Pros:

* More concise and expressive syntax
* Faster execution times due to the use of CSS selectors under the hood
* Supports multiple classes and attributes

Cons:

* Requires support for modern browsers ( Edge 12+, Internet Explorer 11+ )
* Can be slower than `getElementsByClassName` in older browsers that don't support CSS selectors.

**Library/Feature Used**

None, as both methods are part of the native DOM API.

**Special JavaScript Features/Syntax**

No special features or syntax are used in this benchmark. However, it's worth noting that newer versions of JavaScript (e.g., ECMAScript 2015+) have introduced new syntax and features for working with CSS selectors, which might be explored in future benchmarks.

**Other Alternatives**

Alternative methods to retrieve elements by class name include:

* `getElementsByAttribute`: Returns elements whose `class` attribute matches the specified value
* Using a library like jQuery (which provides a `hasClass()` method) or other DOM manipulation libraries that provide more concise and expressive APIs for working with CSS selectors.

Keep in mind that these alternatives might have different performance characteristics, syntax requirements, and browser support compared to `getElementsByClassName` and `querySelector`.

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:92.0) Gecko/20100101 Firefox/92.0

Browser/OS: Firefox 92 on Linux

View result in a separate tab

Test name	Executions per second
getElementById	4048697.0 Ops/sec
querySelector	4106240.2 Ops/sec

Related benchmarks:

getElementById vs querySelectorrthtyj (version: 0)

Comparing performance of: getElementById vs querySelector

Created: 3 years ago by: Guest

Jump to the latest result

getElementById

querySelector

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):