Benchmark: querySelector vs getElementsByClassName

HTML Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

The provided benchmark tests two approaches to selecting an HTML element: `document.querySelector` and `document.getElementsByClassName`. We'll break down each approach, its pros and cons, and discuss any special libraries or features used.

**Approach 1: `document.querySelector`**

`document.querySelector` is a method introduced in ECMAScript 2015 (ES6) that allows you to select an element based on its CSS selector syntax. It's designed to be more efficient than traditional DOM methods, like `getElementsByClassName`.

Pros:

* Faster execution time compared to `getElementsByClassName`
* More readable and maintainable code
* Supports modern JavaScript features

Cons:

* Requires a newer browser (not supported in older browsers like Internet Explorer)
* May have performance issues if the selector is too complex or inefficiently written

**Approach 2: `document.getElementsByClassName`**

`document.getElementsByClassName` is an older method that returns a list of all elements with a specified class name. It's been around since Internet Explorer 4.

Pros:

* Wide browser support (even in older browsers like Internet Explorer)
* Simple and familiar API
* Less prone to performance issues due to its simplicity

Cons:

* Slower execution time compared to `document.querySelector`
* Returns an array of elements, which can be less readable than a single element reference
* May return multiple elements if the class name is not unique

**Library usage**

In this benchmark, there are no libraries used. However, it's worth noting that some libraries like jQuery or CSS selectors might provide similar functionality to `document.querySelector`.

**Special JavaScript feature or syntax**

There are no special features or syntaxes used in this benchmark. The tests use plain old JavaScript and DOM methods.

**Other alternatives**

If you're looking for alternative approaches to selecting elements, here are a few options:

* `document.querySelectorAll`: Similar to `document.querySelector`, but returns a NodeList of all matching elements.
* `Element.prototype.matches()`: Introduced in ECMAScript 2017 (ES7), this method allows you to select elements based on CSS selectors.
* CSS APIs like `CSSOM` or `DOMParser`: Provide more advanced features for working with CSS rules and stylesheets.

In conclusion, the choice between `document.querySelector` and `document.getElementsByClassName` depends on your specific use case, browser support requirements, and personal preference. If you're targeting modern browsers and need more efficient code, `document.querySelector` is likely the better choice. However, if you need to support older browsers or prefer a simpler API, `document.getElementsByClassName` might be a better fit.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36

Browser/OS: Chrome 69 on Windows 7

View result in a separate tab

Test name	Executions per second
querySelector	1186989.2 Ops/sec
getElementsByClassName	1010361.2 Ops/sec

Related benchmarks:

querySelector vs getElementsByClassName (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 6 years ago by: Guest

Jump to the latest result

querySelector

getElementsByClassName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):