Benchmark: document.getElementsByClassname vs document.querySelector

HTML Preparation code:

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

Tests:

Query by class
var test = document.getElementsByClassName('test'); test.innerHTML;
QuerySelector
var test = document.querySelector('.test'); test.innerHTML;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Query by class
QuerySelector

Fastest: N/A

Slowest: N/A

Latest run results:

No previous 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 its implications.

**What is being tested?**

The benchmark compares two different methods for retrieving HTML elements based on their class name:

1. `document.getElementsByClassName('test')`
2. `document.querySelector('.test')`

Both approaches are used to select an HTML element with a class name of "test".

**Options compared:**

* `getElementsByClassName` (implemented in the browser's DOM API)
* `querySelector` (also implemented in the browser's DOM API)

**Pros and Cons:**

* **getElementsByClassName:**
	+ Pros:
		- Typically faster for selecting multiple elements with the same class name.
		- May be more memory-efficient since it returns a NodeList (a live collection of elements).
	+ Cons:
		- Can return multiple elements if there are multiple elements with the same class name on the page.
* **querySelector:**
	+ Pros:
		- Typically faster for selecting a single element, especially when using CSS selectors like `.test`.
		- Returns a single Element object, which can be more convenient to work with than a NodeList.
	+ Cons:
		- May be slower for selecting multiple elements.
		- Requires the use of CSS selectors, which can add complexity.

**Other considerations:**

* **Browser support:** Both `getElementsByClassName` and `querySelector` are widely supported across modern browsers. However, older browsers may not support them, or may have different implementations.
* **Performance differences:** The benchmark results show that `querySelector` is faster than `getElementsByClassName` for selecting a single element in this specific test case.

**Libraries:**

None mentioned in the provided data.

**Special JS feature or syntax:**

None mentioned in the provided data.

**Alternatives:**

Other alternatives for retrieving HTML elements based on their class name include:

* Using an ID selector (e.g., `document.getElementById('id')`)
* Using a CSS selector engine like Sizzle (used by jQuery)
* Writing custom code using a library like Lodash or Underscore.js

However, these alternatives are not being compared in this specific benchmark.

Related benchmarks:

document.getElementsByClassname vs document.querySelector (version: 0)

Comparing performance of: Query by class vs QuerySelector

Created: 5 years ago by: Guest

Jump to the latest result

Query by class

QuerySelector

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):