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document.head vs document.getElementsByTagName("head")[0] fork123
(version: 0)
Benchmark.js
Comparing performance of:
1 vs 2 vs 3
Created:
8 years ago
by:
Guest
Go to the latest result
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>
Run tests (3)
Previous results
Fork
Test case name
Result
1
2
3
Fastest:
N/A
Slowest:
N/A
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/120.0.0.0 Safari/537.36
Browser/OS:
Chrome 120 on Windows
View result in a separate tab
Embed
Embed Benchmark Result
<iframe src="https://measurethat.net/Embed?id=490851" width="100%" height="500px"></iframe>
1
5.7M/s
2
5.2M/s
3
2.5M/s
View exact numbers
Test name
Executions per second
✓
1
5,670,005 Ops/sec
2
5,183,928 Ops/sec
3
2,461,358 Ops/sec
Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
I'll break down the benchmark and its options for you. **Benchmark Definition** The benchmark is designed to compare three different ways of accessing the `<head>` element in an HTML document: 1. `document.head` 2. `document.getElementsByTagName("head")[0]` 3. A combination of both, using the OR operator (`||`). **Options Compared** * Option 1: Direct access to the `<head>` element using `document.head`. + Pros: - Fast and efficient, as it directly accesses a single property. - May be cached by browsers, reducing overhead. + Cons: - May not work in older browsers that don't support `document.head`. * Option 2: Accessing the `<head>` element using `document.getElementsByTagName("head")[0]`. + Pros: - Works in older browsers that don't support `document.head`. - Can provide a fallback if `document.head` is not available. + Cons: - May be slower than direct access, as it involves an extra step to retrieve the first element from the array returned by `getElementsByTagName`. - May incur additional overhead due to the array lookup and iteration. * Option 3: Combination of both using the OR operator (`||`). + Pros: - Provides a single expression that handles both cases (modern browsers and older ones). - Can be more concise than option 2. **Library/ Framework** None explicitly mentioned, but `document` is a part of the DOM (Document Object Model) API, which is a standard API for working with HTML documents in JavaScript. **Special JS Features/Syntax** The benchmark doesn't use any special JavaScript features or syntax beyond what's typically available in modern browsers. However, it does rely on the fact that `document.head` and `document.getElementsByTagName("head")[0]` are properties of the `document` object. **Other Alternatives** If you wanted to test alternative approaches, some possible options could include: * Using `document.querySelector("#myHead")` or `document.getElementById("myHead")` instead of accessing the `<head>` element directly. * Comparing performance with different methods for handling cases where the `<head>` element is not available (e.g., using a fallback element). * Testing the performance impact of using various caching mechanisms, such as memoization or caching in a library. Keep in mind that adding more test cases and alternatives might make the benchmark more complex and harder to maintain.
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