Benchmark: document.head vs document.getElementsByTagName("head")[0]

HTML Preparation code:

<html>
<head id="myHead">
<title>My title</title>
</head>
<body><p id="demo"></p>
</body>
</html>

Tests:

1
var css = document.head || document.getElementsByTagName("head")[0];
2
var css = document.head;
3
var css = document.getElementsByTagName("head")[0];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
1
2
3

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/129.0.0.0 Safari/537.36 Edg/129.0.0.0

Browser/OS: Chrome 129 on Windows

View result in a separate tab

Test name	Executions per second
1	47448372.0 Ops/sec
2	38367028.0 Ops/sec
3	7259132.5 Ops/sec

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

LLMs can make mistakes. Check important info.

Let's dive into the explanation.

**Benchmark Definition**

The benchmark tests the performance of three different approaches to accessing the `<head>` element in an HTML document using JavaScript.

**Test Cases**

There are three test cases:

1. `var css = document.head || document.getElementsByTagName("head")[0];`
2. `var css = document.head;`
3. `var css = document.getElementsByTagName("head")[0];`

These test cases compare the performance of different methods to access the `<head>` element.

**Options Compared**

The three options being compared are:

1. **Using the `document.head` property**: This method returns the `<head>` element directly.
2. **Using `||` operator with `document.head` and `document.getElementsByTagName("head")[0]`**: This method tries to access the `<head>` element using the `document.head` property, and if it fails (for some reason), it falls back to accessing it using `document.getElementsByTagName("head")[0]`.
3. **Using `document.getElementsByTagName("head")[0]` directly**: This method accesses the `<head>` element by getting all elements with the tag name "head" and taking the first one.

**Pros and Cons**

Here are some pros and cons of each approach:

1. **Using `document.head` property**:
	* Pros: Easy to read, concise code.
	* Cons: Might be slower than other methods since it relies on the browser's implementation.
2. **Using `||` operator with `document.head` and `document.getElementsByTagName("head")[0]`**:
	* Pros: Provides a fallback mechanism in case `document.head` is not supported or fails.
	* Cons: Might introduce performance overhead due to the additional check.
3. **Using `document.getElementsByTagName("head")[0]` directly**:
	* Pros: Guaranteed to work even if `document.head` is not available.
	* Cons: Less concise code, might be slower than other methods since it involves getting all elements with the tag name "head".

**Other Considerations**

The choice of method depends on the specific use case. If you're targeting browsers that support `document.head`, using that property directly might be the best approach. However, if you need to ensure compatibility across older browsers or edge cases, using the `||` operator with a fallback mechanism might be more suitable.

**Library**

No external libraries are used in these test cases.

**Special JS feature or syntax**

No special JavaScript features or syntax are used in these test cases.

**Alternatives**

Some alternative approaches to accessing the `<head>` element include:

1. Using `document.querySelector("head")`: This method uses a CSS selector to get the first `<head>` element.
2. Using `document.getElementById("head-id")`: If you have an `<head>` element with a specific ID, you can use this method to access it directly.

These alternatives might be faster or more efficient in certain scenarios, but they also depend on the specific requirements and constraints of your project.

Related benchmarks:

document.head vs document.getElementsByTagName("head")[0] (version: 0)

Comparing performance of: 1 vs 2 vs 3

Created: 7 years ago by: Guest

Jump to the latest result

1

2

3

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):