Benchmark: Regex type checking comparison

Script Preparation code:

var regex = /[a-z]/i;

Tests:

instanceof
regex instanceof RegExp
test property
!!regex.test

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
test property

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 months 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

Browser/OS: Chrome 129 on Windows

View result in a separate tab

Test name	Executions per second
instanceof	7587502.0 Ops/sec
test property	19638160.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of MeasureThat.net and understand what's being tested in this benchmark.

**What is tested?**

The provided JSON represents a JavaScript microbenchmark that compares two different approaches to check if a variable `regex` is an instance of the `RegExp` class. There are two test cases:

1. **"instanceof"**: This test case checks if `regex instanceof RegExp`.
2. **"test property"**: This test case checks if the `test` property of the `regex` object returns true.

**Options compared**

The benchmark compares the performance of two approaches to check if a variable is an instance of the `RegExp` class:

1. **Using `instanceof` operator**: This approach uses the `instanceof` operator (`regex instanceof RegExp`) to check if `regex` is an instance of `RegExp`.
2. **Using `test` property**: This approach checks if the `test` property of the `regex` object returns true.

**Pros and cons of each approach**

* **Using `instanceof` operator**:
	+ Pros: Simple, straightforward, and widely supported.
	+ Cons: Can be slower than using a method like `test()` on non-RegExp values, as it requires a more complex type check.
* **Using `test` property**:
	+ Pros: Can be faster for non-RegExp values, as it only checks if the value has a `test()` method without needing to perform a full instance check.
	+ Cons: May return unexpected results if the `test` property is not defined or is set to an incorrect value. Additionally, this approach may not work correctly on all browsers or environments.

**Library usage**

There is no explicit library mentioned in the benchmark definition or test cases. However, it's worth noting that the use of the `RegExp` class and its properties like `test()` might rely on built-in JavaScript functionality.

**Special JS feature or syntax**

The benchmark does not explicitly mention any special JavaScript features or syntax. The use of `instanceof`, `RegExp`, and `test` property is standard JavaScript syntax.

**Other alternatives**

If you're interested in exploring alternative approaches to check if a variable is an instance of the `RegExp` class, here are a few options:

1. **Using `constructor.name`**: In modern browsers (e.g., Chrome 129), you can use `regex.constructor.name === 'RegExp'` to check if `regex` is an instance of `RegExp`.
2. **Using a library like Lodash**_: If you prefer a more functional approach, you could use the `isRegExp` function from Lodash _.isRegExp(regex)` to check if `regex` is an instance of `RegExp`.

Keep in mind that these alternatives might have different performance characteristics or behave differently across browsers and environments.

I hope this explanation helps!

Related benchmarks:

Regex type checking comparison (version: 0)

Comparing performance of: instanceof vs test property

Created: one year ago by: Guest

Jump to the latest result

instanceof

test property

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):