Benchmark: getElementById + getElementByClassName vs querySelector

HTML Preparation code:

<div id="testElement">
  <div class="testElementChild1">1</div>
  <div class="testElementChild2">2</div>
  <div class="testElementChild3">3</div>
  <div class="testElementChild4">4</div>
  <div class="testElementChild5">5</div>
</div>

Script Preparation code:

var doc = document;
var testElement = doc.getElementById('testElement');

Tests:

getElementsById + getElementsByClassName
var test = doc.getElementById('testElement').getElementsByClassName('testElementChild3').innerHTML;
querySelector + querySelector
var test = doc.querySelector('#testElement').querySelector('.testElementChild3').innerHTML;
querySelector
var test = doc.querySelector('#testElement .testElementChild3').innerHTML;
cache + getElementsByClassName
var test = testElement.getElementsByClassName('testElementChild3').innerHTML;
cache + querySelector
var test = testElement.querySelector('.testElementChild3').innerHTML;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementsById + getElementsByClassName
querySelector + querySelector
querySelector
cache + getElementsByClassName
cache + querySelector

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the details of what's being tested on MeasureThat.net.

**Benchmark Overview**

The benchmark is designed to compare the performance of different approaches for selecting elements in an HTML document. The test cases are designed to measure the execution time of various JavaScript methods, including:

1. `getElementById + getElementsByClassName`
2. `querySelector + querySelector`
3. `querySelector` (without `+ querySelector`)
4. `cache + getElementsByClassName`
5. `cache + querySelector`

**What's being tested**

Each test case measures the execution time of a specific JavaScript method that retrieves an element from the HTML document and extracts its inner HTML.

Here's what each test case does:

1. `getElementById + getElementsByClassName`: Retrieves the `testElement` using `document.getElementById('testElement')`, and then uses `getElementsByClassName('testElementChild3')` to retrieve all elements with the class `testElementChild3`. Finally, it extracts the inner HTML of the first element.
2. `querySelector + querySelector`: Uses `document.querySelector('#testElement')` to select an element with the id `testElement`, and then uses `querySelector('.testElementChild3')` to select a child element with the class `testElementChild3`. Finally, it extracts the inner HTML of the selected element.
3. `querySelector`: Similar to the previous test case, but without using `+ querySelector`.
4. `cache + getElementsByClassName`: Uses `document.getElementById('testElement').getElementsByClassName('testElementChild3')` as a cached value to retrieve all elements with the class `testElementChild3`, and then extracts their inner HTML.
5. `cache + querySelector`: Similar to the previous test case, but using a cached value for `querySelector`.

**Pros and Cons of each approach**

Here's a brief analysis of each approach:

1. **`getElementById + getElementsByClassName`**: This approach is simple and straightforward, but it can be slower than other methods because it uses two separate calls to retrieve elements.
2. **`querySelector + querySelector`**: This approach is faster than the previous one because it uses a single call to `querySelector`, which reduces overhead. However, it requires more complex CSS selectors, which can be error-prone.
3. **`querySelector`**: Similar to the previous test case, but without using `+ querySelector`. This approach is faster and more concise than the first two, but may require more browser support for modern CSS selectors.
4. **`cache + getElementsByClassName`**: This approach uses a cached value to retrieve elements with the class `testElementChild3`, which can reduce overhead and improve performance. However, it requires extra memory allocation and can be slower than using `querySelector`.
5. **`cache + querySelector`**: Similar to the previous test case, but using a cached value for `querySelector`. This approach combines the benefits of caching with the speed of `querySelector`.

**Library and syntax considerations**

In this benchmark, no specific libraries or frameworks are used beyond the standard HTML document object model (DOM).

The only JavaScript feature used is template literals (`var test = ...;`), which allow for concise string interpolation.

No special JavaScript features like `async/await`, `Promises`, or modern syntax are used in these test cases.

**Alternatives**

If you're looking to optimize your code for performance, consider the following alternatives:

1. **Use a CSS query builder**: Instead of using `querySelector` with multiple selectors, use a library like [css-query-builder](https://github.com/css-query_builder/css-query-builder) or implement your own query builder.
2. **Caching libraries**: Use caching libraries like [cache-manager](https://github.com/webpack/cache-manager) to optimize performance and reduce overhead.
3. **Code splitting**: Split your code into smaller chunks using code splitting techniques, which can improve performance by reducing the amount of code that needs to be executed.

Keep in mind that these alternatives may require additional setup and configuration, but they can provide significant performance benefits for complex applications.

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/102.0.0.0 Safari/537.36

Browser/OS: Chrome 102 on Windows

View result in a separate tab

Test name	Executions per second
getElementsById + getElementsByClassName	2167442.8 Ops/sec
querySelector + querySelector	1372145.2 Ops/sec
querySelector	1909224.9 Ops/sec
cache + getElementsByClassName	2477965.5 Ops/sec
cache + querySelector	2492925.0 Ops/sec

Related benchmarks:

getElementById + getElementByClassName vs querySelector (version: 0)

getElementById + getElementByClass vs querySelector

Comparing performance of: getElementsById + getElementsByClassName vs querySelector + querySelector vs querySelector vs cache + getElementsByClassName vs cache + querySelector

Created: 4 years ago by: Guest

Jump to the latest result

getElementsById + getElementsByClassName

querySelector + querySelector

querySelector

cache + getElementsByClassName

cache + querySelector

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):