Benchmark: querySelector vs getElementsByClassName fixed

HTML Preparation code:

<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:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.134 Safari/537.36

Browser/OS: Chrome 103 on Windows

View result in a separate tab

Test name	Executions per second
querySelector	5491866.0 Ops/sec
getElementsByClassName	5175431.5 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain what's being tested in the provided benchmark.

The test is comparing two DOM querying methods: `document.querySelector()` and `document.getElementsByClassName()`. Specifically, it's measuring the performance of these methods when searching for elements with a class name of "test".

**Options compared:**

* `document.querySelector(".test")`: This method uses the `querySelector` API to select an element based on its CSS selector. In this case, the selector is `.test`, which matches any element that has at least one descendant that has a class name of "test".
* `document.getElementsByClassName("test")`: This method returns a live HTMLCollection of all elements with the specified class name.

**Pros and cons:**

* **`document.querySelector()`**: Pros:
	+ More efficient for selecting single elements.
	+ Can be used to select multiple elements using more complex CSS selectors.
	+ Works well with modern browsers that support it.
* Cons:
	+ May not work as expected in older browsers that don't support `querySelector`.
	+ Can be slower than `getElementsByClassName` because it needs to parse the CSS selector.
* **`document.getElementsByClassName()`**: Pros:
	+ Works consistently across all browsers, including older ones.
	+ Returns a live collection of elements, which means you can iterate over them without creating a new array.
* Cons:
	+ Can be slower than `querySelector` for selecting single elements.
	+ Requires more code to filter or manipulate the results.

**Library usage:**

Neither of these methods uses any external libraries. They are built-in DOM APIs that are available in most JavaScript engines.

**Special JS feature or syntax:**

There is no special JavaScript feature or syntax being used in this benchmark. The focus is solely on comparing two DOM querying methods.

**Other alternatives:**

If you need to query elements based on other attributes, such as an ID or a property value, you might consider using `document.getElementById()` (for IDs) or `element.getAttribute()` (for attribute values). For more complex queries, you can use CSS selectors with the `querySelectorAll()` method.

For example, if you wanted to select all elements with both a class name of "test" and an ID of "myId", you could use:
```javascript
const elements = document.querySelectorAll(".test#myId");
```
Keep in mind that this is just one possible way to solve the problem. The choice of method depends on your specific requirements and the characteristics of your data.

Related benchmarks:

querySelector vs getElementsByClassName fixed (version: 0)

Comparing performance of: querySelector vs getElementsByClassName

Created: 2 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 2 months ago):