Benchmark: querySelector vs getElementsByClassName

HTML Preparation code:

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

Tests:

querySelector
document.querySelectorAll(".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:

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Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

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Let's dive into the benchmark definition and results.

**Benchmark Definition**

The benchmark measures the performance difference between two DOM querying methods: `document.querySelectorAll` and `document.getElementsByClassName`.

**Test Cases**

There are two test cases:

1. **querySelector**: This test case uses the `document.querySelectorAll` method to select an element with class "test" from the HTML preparation code.
2. **getElementsByClassName**: This test case uses the `document.getElementsByClassName` method to select an element with class "test" from the same HTML preparation code.

**Library**

No external libraries are used in this benchmark.

**JS Features/Syntax**

The benchmark uses two DOM querying methods, which are built-in JavaScript features:

1. **querySelectorAll**: Returns a NodeList of elements that match the specified CSS selector.
2. **getElementsByClassName**: Returns an HTMLCollection of elements with the specified class name.

These methods allow developers to select and manipulate elements in the Document Object Model (DOM) using CSS-like selectors.

**Options Compared**

The benchmark compares two approaches:

1. **querySelectorAll**: This method returns a NodeList, which is a collection of Node objects.
2. **getElementsByClassName**: This method returns an HTMLCollection, which is also a collection of Node objects.

**Pros/Cons**

Here are some pros and cons of each approach:

1. **querySelectorAll**
	* Pros:
		+ Can use CSS selectors to select elements (e.g., `.test`, `#id`)
		+ Returns a NodeList, which can be easily iterated or manipulated
	* Cons:
		+ May be slower than getElementsByClassName for simple class name queries
2. **getElementsByClassName**
	* Pros:
		+ Typically faster than querySelectorAll for simple class name queries
		+ Returns an HTMLCollection, which is a collection of Node objects
	* Cons:
		+ Only returns elements with the specified class name (no CSS selectors)
		+ May not work correctly if the document contains multiple matching elements

**Other Considerations**

When choosing between querySelectorAll and getElementsByClassName, consider the following:

1. **Complexity**: If you need to select elements using complex CSS selectors, use querySelectorAll.
2. **Performance**: If performance is critical, use getElementsByClassName for simple class name queries.
3. **Iteration**: If you need to iterate over the selected elements, use a NodeList (returned by querySelectorAll).

**Other Alternatives**

In addition to these two methods, there are other ways to select and manipulate elements in the DOM:

1. **document.getElementById**: Returns a single element with the specified ID.
2. **document.getElementsByTagName**: Returns an HTMLCollection of elements with the specified tag name.

These alternatives may be useful depending on your specific use case. However, querySelectorAll and getElementsByClassName are generally more versatile and widely supported in modern browsers.

Related benchmarks:

querySelector vs getElementsByClassName (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 8 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 llama3.1:latest, generated one year ago):