Benchmark: cssRule Identify the type

HTML Preparation code:

<html>
<style>
    html {
    color: red;
      }
</style>

</html>

Script Preparation code:

window.myRules = document.styleSheets[0].cssRules;

Tests:

type
myRules[0].type === 1
instanceof
myRules[0] instanceof CSSStyleRule
toString
myRules[0].toString() === '[object CSSStyleRule]'

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
type
instanceof
toString

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.159 Safari/537.36

Browser/OS: Chrome 92 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
type	9391044.0 Ops/sec
instanceof	5220624.5 Ops/sec
toString	8250070.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark and explore the options, pros, cons, and other considerations.

**Benchmark Definition**

The benchmark is testing the type of a CSS rule on a web page. Specifically, it creates a stylesheet and retrieves its first rule using `window.myRules = document.styleSheets[0].cssRules;`. The benchmark then checks three different conditions:

1. `myRules[0].type === 1`
2. `myRules[0] instanceof CSSStyleRule`
3. `myRules[0].toString() === '[object CSSStyleRule]'`

These conditions test whether the rule is of type 1 (a `CSSStyleRule`), an instance of `CSSStyleRule`, and whether its string representation matches the expected format.

**Options compared**

The benchmark is comparing three different approaches to check the type of a CSS rule:

1. **Type checking (`myRules[0].type === 1`)**: This checks if the `type` property of the rule is exactly equal to 1.
2. **Instance checking (`myRules[0] instanceof CSSStyleRule`)**: This checks if the rule is an instance of the `CSSStyleRule` class.
3. **String representation check (`myRules[0].toString() === '[object CSSStyleRule]'`)**: This checks if the string representation of the rule matches a specific format.

**Pros and Cons**

1. **Type checking**: Pros - simple, fast, cons - may not work correctly if the `type` property is not what you expect.
2. **Instance checking**: Pros - more robust than type checking, cons - slower due to dynamic typing checks.
3. **String representation check**: Pros - provides additional information about the rule, cons - may require special handling for non-standard rules.

**Library and its purpose**

The `CSSStyleRule` class is a part of the Web API, which allows JavaScript to manipulate CSS stylesheets on web pages.

**Special JS feature or syntax**

None mentioned in this benchmark.

**Other considerations**

* Using `instanceof` can be slower than type checking because it involves dynamic typing checks.
* The `toString()` method may return different results for non-standard rules.
* The `type` property is not always equal to 1, even if the rule is a `CSSStyleRule`.

**Alternatives**

Other ways to check if an element is a CSS rule include:

* Using a library like `css-select` or `css-tree` to parse the stylesheet and extract the rules.
* Creating a custom function that checks for specific characteristics of a CSS rule.

Keep in mind that these alternatives may introduce additional complexity, overhead, or dependencies.

Related benchmarks:

cssRule Identify the type (version: 0)

Comparing performance of: type vs instanceof vs toString

Created: 3 years ago by: Registered User

Jump to the latest result

type

instanceof

toString

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):