Benchmark: childNodes vs children vs firstChild vs firstElementChild

HTML Preparation code:

<html>

<body>
    <div id='test'>
        <div name='a'></div>
        <div name='b'></div>
        <div name='c'></div>
    </div>
</body>

</html>

Script Preparation code:

var parent = document.getElementById('test');

Tests:

childNodes[0]
let n = parent.childNodes[0];
children[0]
let n = parent.children[0];
firstChild
let n = parent.firstChild;
firstElementChild
let n = parent.firstElementChild;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
childNodes[0]
children[0]
firstChild
firstElementChild

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Linux

View result in a separate tab

Test name	Executions per second
childNodes[0]	10484387.0 Ops/sec
children[0]	10450944.0 Ops/sec
firstChild	17028428.0 Ops/sec
firstElementChild	16418841.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided JSON represents a JavaScript microbenchmark that measures the performance of four different ways to list children in an HTML element: `childNodes`, `children`, `firstChild`, and `firstElementChild`. The benchmark is designed to test which approach is the fastest.

**Options Compared**

The benchmark compares the following options:

1. **childNodes**: This method returns a live HTMLCollection of all child nodes, including text nodes, comment nodes, and other nodes.
2. **children**: This method also returns an HTMLCollection of all direct child elements of the parent element.
3. **firstChild**: This method returns the first child node of the parent element, or null if there are no children.
4. **firstElementChild**: This method returns the first element child of the parent element, or null if there are no element children.

**Pros and Cons of Each Approach**

1. **childNodes**:
	* Pros: Returns all child nodes, including text and comment nodes.
	* Cons: Can be slow for large numbers of nodes due to the need to iterate over all nodes.
2. **children**:
	* Pros: Faster than `childNodes` for element children only, as it doesn't need to iterate over non-element nodes.
	* Cons: Returns both element and non-element child nodes, which may not be desirable in all cases.
3. **firstChild**:
	* Pros: Fast and efficient for retrieving the first child node.
	* Cons: Returns null if there are no children, which may require additional checks.
4. **firstElementChild**:
	* Pros: Similar to `firstChild`, but returns an element node instead of a node object.
	* Cons: May return null if there are no element children.

**Library Usage**

There is no explicit library usage in this benchmark. However, the `HTMLCollection` interface used by all four options is part of the W3C DOM specification and is widely supported across modern browsers.

**Special JS Features or Syntax**

None of the options use any special JavaScript features or syntax beyond the standard DOM API methods.

**Alternative Approaches**

For larger datasets or performance-critical applications, alternative approaches may include:

1. **Using a library like Lodash**: Lodash provides a `forEach` method that can be used to iterate over arrays (including HTMLCollections), which could potentially improve performance.
2. **Using a more efficient data structure**: For large datasets, using a more efficient data structure like an array or a Set might reduce the time complexity of accessing elements.
3. **Optimizing the DOM tree**: In some cases, optimizing the DOM tree by adding event listeners or using other optimization techniques can improve performance.

However, these alternatives may not be applicable in this specific benchmark, as it is focused on comparing the basic methods provided by the DOM API.

Related benchmarks:

childNodes vs children vs firstChild vs firstElementChild (version: 0)

Fastest way to list children

Comparing performance of: childNodes[0] vs children[0] vs firstChild vs firstElementChild

Created: 3 years ago by: Guest

Jump to the latest result

childNodes[0]

children[0]

firstChild

firstElementChild

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):