Benchmark: document.getElementById vs GetChildElementById

HTML Preparation code:

<!DOCTYPE html>
<html>
  <head>
  </head>
  <body>
    <div id="parent" class="parent_class">
      AAA
      <div id="child" class="child_class">
        content
      </div>
      BBB
    </div>
  </body>
</html>

Script Preparation code:

/**
 * Function will get element by id starting from specified node.
 * Author: Renato Bebić <renato.bebic@gmail.com>
 *
 */
function GetChildElementById(dNode, id) {
	var dResult = null;

	if (dNode.getAttribute('id') == id)
		return dNode;

	for (var i = 0; i < dNode.childNodes.length; i++) {
		if (dNode.childNodes[i].nodeType == 1) {
			dResult = GetChildElementById(dNode.childNodes[i], id);
			if (dResult != null)
				break;
		}
	}

	return dResult;
}

Tests:

Native method
var el = document.getElementById('child'); var className = el.className;
Custom method
var x = document.getElementById('parent'); var el = GetChildElementById(x, 'child'); var className = el.className;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Native method
Custom method

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36

Browser/OS: Chrome 117 on Windows

View result in a separate tab

Test name	Executions per second
Native method	5078349.0 Ops/sec
Custom method	1290435.8 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript benchmarks.

**Benchmark Definition**

The provided JSON represents a benchmark test case that compares two methods for retrieving an element by its ID: `document.getElementById` (native method) and `GetChildElementById` (custom method).

**Native Method (`document.getElementById`)**

This method is a built-in part of the DOM API in JavaScript. It takes an ID as a string argument and returns the element that matches that ID, or `null` if no matching element is found.

The pros of using this method are:

1. **Efficiency**: This method is highly optimized by browsers to provide fast results.
2. **Convenience**: It's a straightforward and easy-to-use method for getting an element by its ID.

However, there are some potential cons:

1. **Limited control**: Since it's a built-in method, you have limited control over the implementation details.
2. **Browser quirks**: Different browsers might implement this method slightly differently, which could affect performance.

**Custom Method (`GetChildElementById`)**

This is a custom function that recursively traverses the DOM tree to find an element with the specified ID.

The pros of using this method are:

1. **Control**: By writing your own implementation, you have full control over how the algorithm works.
2. **Flexibility**: You can modify or extend the implementation as needed.

However, there are some potential cons:

1. **Performance overhead**: Recursively traversing the DOM tree can be slower than using a built-in method like `document.getElementById`.
2. **Complexity**: The implementation needs to handle various edge cases and corner scenarios, which can increase complexity.

**Library**

In the provided benchmark, the `GetChildElementById` function uses the `getAttribute` method from the DOM API to retrieve the ID of an element. This is a standard part of the DOM API in JavaScript.

No additional libraries are required for this test case.

**Special JS Features or Syntax**

There are no special features or syntax used in this benchmark that would require specific knowledge of advanced JavaScript concepts. The implementation is straightforward and easy to follow.

**Alternatives**

If you're interested in exploring alternative methods for retrieving an element by its ID, here are a few options:

1. **QuerySelector**: This method uses CSS selectors to retrieve elements. It's faster than `document.getElementById` but requires more knowledge of CSS syntax.
2. **querySelectorAll**: This method returns a list of all elements that match the specified selector. You can use this method to retrieve multiple elements at once.

In summary, the benchmark tests two common methods for retrieving an element by its ID: `document.getElementById` (native method) and `GetChildElementById` (custom method). The native method is highly optimized but has limited control, while the custom method provides more control but may incur performance overhead.

Related benchmarks:

document.getElementById vs GetChildElementById (version: 0)

Comparing speed of getting element by id with two different methods.

Comparing performance of: Native method vs Custom method

Created: 6 years ago by: Guest

Jump to the latest result

Native method

Custom method

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):