Benchmark: querySelector vs getElementsByClassName with multiple matching nodes

HTML Preparation code:

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

Tests:

querySelector
document.querySelector(".test")
getElementsByClassName
document.getElementsByClassName(".test")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector
getElementsByClassName

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its options.

**Benchmark Definition**

The website is testing two JavaScript methods: `document.querySelector` and `document.getElementsByClassName`. These methods are used to select elements from a HTML document using CSS selectors or class names.

**Options being compared**

* `document.querySelector`: This method takes a CSS selector as an argument and returns the first element that matches the selector. In this benchmark, it's being tested with the `.test` class name.
* `document.getElementsByClassName`: This method also takes a CSS class name as an argument, but it returns all elements that match the class name, not just the first one.

**Pros and Cons**

* **Performance:** `document.querySelector` is generally faster than `document.getElementsByClassName`, especially when only matching one element. This is because `querySelector` can stop searching for matches as soon as it finds the first one, whereas `getElementsByClassName` continues searching until it has found all elements that match.
* **Flexibility:** `getElementsByClassName` returns a NodeList (a collection of nodes), which allows you to access and manipulate multiple elements at once. However, this can also lead to slower performance if not used carefully.
* **Error handling:** If no element matches the selector, `querySelector` will return `null`, whereas `getElementsByClassName` will return an empty NodeList.

**Library**

There is no explicit library being tested in this benchmark. Both methods are built-in functions of the Document Object Model (DOM).

**Special JavaScript Feature/ Syntax**

There isn't any special feature or syntax being used in this benchmark, apart from the use of CSS selectors and class names.

**Other Alternatives**

If you needed to select elements differently, you could consider using other methods such as:

* `document.querySelectorAll`: Similar to `querySelector`, but returns a NodeList that matches multiple selectors.
* `Array.from()`: Can be used with an array of class names or selectors to create an array of matching elements.
* `Element.prototype.matches()`: (Available in modern browsers) allows you to use CSS selectors to select elements.

Keep in mind that each method has its own trade-offs and performance characteristics, so it's essential to choose the right one depending on your specific use case.

Related benchmarks:

querySelector vs getElementsByClassName with multiple matching nodes (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>

Fastest: N/A

Slowest: N/A

No previous run results

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