Benchmark: isArray vs length2

Script Preparation code:

function myIsArray(obj){
  return 'length' in obj;
}

var isArray = Array.isArray

Tests:

Array.isArray
isArray([])
Check object.length
myIsArray([])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.isArray
Check object.length

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the test case and explain what's being tested.

**Benchmark Definition**

The benchmark definition is a JSON object that describes the test. In this case, it includes:

* `Name`: A unique name for the benchmark (in this case, "isArray vs length2").
* `Description`: A brief description of the test.
* `Script Preparation Code`: The JavaScript code that prepares the environment for the test. In this case, two functions are defined:
	+ `myIsArray(obj)`: A custom function that checks if an object is an array using the `in` operator on the `length` property. This is done to simulate how a developer might write their own array check.
	+ `isArray`: The built-in `Array.isArray()` method, which is being compared with the custom implementation.
* `Html Preparation Code`: An empty string, indicating that no HTML-related setup is required.

**Individual Test Cases**

The test cases are defined as an array of objects. In this case, there are two test cases:

1. `"isArray([])"`:
	* This test checks how different browsers handle the `Array.isArray()` method when passed an empty array (`[]`).
2. `"myIsArray([])"`:
	* This test checks how different browsers handle the custom implementation of `myIsArray(obj)` for an empty array (`[]`). The purpose of this test is to compare the performance of the built-in `Array.isArray()` method with a custom implementation.

**Library and Purpose**

The library being used here is the `Array` class, which provides various methods for working with arrays. In this case, the `Array.isArray()` method is being compared with a custom implementation.

**Special JS Feature or Syntax**

There are no special JavaScript features or syntax mentioned in this test case. However, it's worth noting that the use of `in` operator on the `length` property is an older way to check if a value is an array (although not recommended for new code). The built-in `Array.isArray()` method is generally considered more reliable and efficient.

**Pros and Cons of Different Approaches**

Here are some pros and cons of each approach:

* **Built-in `Array.isArray()` method**: Pros:
	+ More reliable and efficient
	+ Less prone to errors (e.g., using the wrong value)
	+ Part of the standard library, so it's widely supported
	Cons:
	+ May not be as fast as custom implementations for specific use cases
* **Custom implementation (`myIsArray(obj)`)**: Pros:
	+ Can potentially be faster than the built-in method for specific use cases (e.g., small arrays)
	+ Allows for more control over the implementation
	Cons:
	+ More prone to errors and inconsistencies
	+ May not be as widely supported or reliable

**Other Considerations**

When writing benchmarks, it's essential to consider factors like:

* **Test scope**: Ensure that the test is relevant and representative of real-world use cases.
* **Benchmarking methodology**: Choose a suitable benchmarking library or tool (e.g., MeasureThat.net) that can accurately measure performance.
* **Browser variations**: Include multiple browser versions and platforms to ensure that the results are representative of different user bases.

**Alternatives**

Other alternatives for testing array checks include:

* Using a benchmarking library like Benchmark.js
* Writing custom tests using Jest, Mocha, or another testing framework
* Utilizing tools like WebPageTest or BrowserStack for more comprehensive testing

These alternatives can provide additional insights and help ensure that the results are accurate and representative of real-world performance.

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/109.0.0.0 Safari/537.36

Browser/OS: Chrome 109 on Windows

View result in a separate tab

Test name	Executions per second
Array.isArray	21091926.0 Ops/sec
Check object.length	21021094.0 Ops/sec

Related benchmarks:

isArray vs length2 (version: 0)

Array.isArray vs array.length > 0

Comparing performance of: Array.isArray vs Check object.length

Created: one year ago by: Guest

Jump to the latest result

Array.isArray

Check object.length

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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