Benchmark: parent contain child

HTML Preparation code:

<div id="parent"><div id="child"></div></div>

Script Preparation code:

var parent = document.getElementById("parent");
var child = document.getElementById("child");

Tests:

contains
parent.contains(child);
selector
parent.querySelectorAll("#child").length;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
contains
selector

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

Let's dive into the world of MeasureThat.net, where we can analyze and compare the performance of different approaches to JavaScript microbenchmarks.

**Benchmark Definition**

The provided Benchmark Definition json represents a simple benchmark that tests two approaches:

1. **`parent.contains(child)`**: This approach uses the `contains()` method on the `parent` element's DOMNode object to check if it contains a child node with the ID "child".
2. **`parent.querySelectorAll("#child").length`**: This approach uses the `querySelectorAll()` method on the `parent` element's DOMDocument object to select all elements that match the CSS selector "#child" and returns an array of nodes. The length property is then accessed to get the number of matching elements.

**Options Compared**

The two approaches are compared in terms of performance, with each approach having its own pros and cons:

*   **`parent.contains(child)`**: This approach is generally faster and more efficient because it only checks if the parent element contains a child node without actually querying the DOM. However, it may not work correctly if the `child` element has any ancestors that also contain other elements.
*   **`parent.querySelectorAll("#child").length`**: This approach is slower and less efficient because it actually queries the DOM to find all elements that match the CSS selector "#child". While this approach can be useful in certain situations, it may not be suitable for large-scale web applications where DOM query performance is critical.

**Pros and Cons of Each Approach**

*   **`parent.contains(child)`**: Pros:
    *   Generally faster and more efficient
    *   Can be used with any element as the parent or child
    *   Reduces memory usage by avoiding unnecessary DOM node creation
*   Cons:
    *   May not work correctly if the `child` element has ancestors that also contain other elements
*   **`parent.querySelectorAll("#child").length`**: Pros:
    *   Can be useful in situations where exact matching is required (e.g., selecting all descendants of an element)
    *   Allows for more flexibility with CSS selectors
*   Cons:
    *   Generally slower and less efficient due to DOM query overhead
    *   Creates unnecessary DOM nodes that need to be garbage collected

**Library Used**

The provided benchmark definition does not use any external libraries or frameworks. The JavaScript code is self-contained and relies only on the built-in `document` object.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntax used in this benchmark definition. It uses standard ECMAScript 2015+ syntax, including template literals (`\r\n`) for concatenating strings.

**Alternatives**

For comparing performance of different approaches to DOM queries and element containment, other alternatives include:

*   **`Element.contains()`**: This method is similar to `contains()` but can also be used with element references rather than node references.
*   **`Array.prototype.includes()`**: This method can be used to check if an array includes a specific value or another array.
*   **QuerySelectorAll()**: This method can be used in combination with the `querySelector` method to select elements based on CSS selectors.

However, for most web applications, using `parent.contains(child)` and avoiding unnecessary DOM queries will generally provide better performance.

Related benchmarks:

parent contain child (version: 0)

Comparing performance of: contains vs selector

Created: 9 years ago by: Registered User

Jump to the latest result

contains

selector

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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