Benchmark: querySelectorAll vs getElementsByClassName naid iteration

HTML Preparation code:

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

Tests:

querySelectorAll
const allDivs = document.querySelectorAll('div'); allDivs.forEach(function (div) {});
getElementsByTagName
const allDivs = document.getElementsByClassName('div'); const arrayAllDivs = Array.from(allDivs); arrayAllDivs.forEach(function (div) {});

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelectorAll
getElementsByTagName

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.102 Safari/537.36

Browser/OS: Chrome 98 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelectorAll	379849.5 Ops/sec
getElementsByTagName	301758.1 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared, and the pros/cons of each approach.

**Benchmark Overview**

The benchmark is comparing two methods to retrieve an array of HTML elements: `querySelectorAll` and `getElementsByTagName`. The test case creates a simple HTML page with multiple `<div>` elements and measures the performance difference between these two methods.

**Options Compared**

1. **`querySelectorAll`**: This method uses a CSS selector to select all elements that match the specified query string.
2. **`getElementsByTagName`**: This method returns a live HTMLCollection of all elements with the specified tag name.

**Pros/Cons of Each Approach**

1. **`querySelectorAll`**:
	* Pros: Efficient, fast, and widely supported by modern browsers.
	* Cons: May be slower for very large sets of elements due to CSS parser overhead.
2. **`getElementsByTagName`**:
	* Pros: Faster for very large sets of elements since it uses a native DOM method.
	* Cons: Less efficient than `querySelectorAll`, may not work in older browsers, and can be less readable.

**Library and Syntax**

There is no library mentioned in the benchmark. Both methods are built-in to JavaScript and do not require any external libraries.

**Special JS Feature/Syntax**

None mentioned.

**Other Considerations**

* The test case uses `Array.from()` to convert the HTMLCollection returned by `getElementsByTagName` into an array, which may incur additional overhead.
* The `forEach()` method is used for iteration in both test cases, but it's worth noting that using `forEach()` can lead to unnecessary DOM traversals if not optimized.

**Alternatives**

Other methods for retrieving arrays of elements include:

1. **`document.querySelectorAll()` with a CSS selector**: This method is similar to `querySelectorAll`, but allows for more advanced CSS selectors.
2. **`Element.all()` in older browsers**: Some older browsers, like Internet Explorer 11, use this method to retrieve an array of elements.

In summary, the benchmark is testing the performance difference between two methods for retrieving arrays of HTML elements: `querySelectorAll` and `getElementsByTagName`. While both methods have their pros and cons, `querySelectorAll` is generally considered more efficient and widely supported.

Related benchmarks:

querySelectorAll vs getElementsByClassName naid iteration (version: 0)

Comparing performance of: querySelectorAll vs getElementsByTagName

Created: 2 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByTagName

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):