Benchmark: isArray vs optional length 2

Script Preparation code:

function myIsArray(obj){
  return obj?.length > 0;
}

var isArray = Array.isArray

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Check Array.isArray([])
Check object?.length
Check Array.isArray(null)
Check null?.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 benchmark and its various components.

**Benchmark Definition**

The provided JSON represents a JavaScript microbenchmark, which is a small piece of code designed to measure the performance of specific parts of JavaScript. The main part of the benchmark definition is:

```json
{
  "Name": "isArray vs optional length 2",
  "Description": "Array.isArray vs array?.length > 0"
}
```

This defines two functions: `myIsArray` and `isArray`. Both functions take an object as input and return a boolean value. The main difference between them is that:

*   `myIsArray(obj)` returns `true` if the input `obj` has a `.length` property greater than 0, but does not check whether it's actually an array.
*   `isArray(obj)` uses the built-in `Array.isArray()` method to check if the input `obj` is indeed an array.

**Options Compared**

The benchmark compares the performance of these two approaches:

1.  Using a custom function (`myIsArray`) with optional chaining (`?.`)
2.  Using the built-in `Array.isArray()` method

These options are compared in different test cases, which will be explained later.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

*   **Using a custom function (`myIsArray`) with optional chaining (`?.`):**
    *   Pros:
        *   More flexible, as it allows for additional checks or operations.
        *   Can be more readable if you're familiar with its syntax.
    *   Cons:
        *   Might incur overhead due to the additional check and optional chaining operations.
        *   Less maintainable, as changes might affect multiple parts of your codebase.
*   **Using the built-in `Array.isArray()` method:**
    *   Pros:
        *   Very lightweight and efficient, as it's a native JavaScript function.
        *   Easy to read and understand for developers familiar with its syntax.
    *   Cons:
        *   Less flexible than the custom approach, as you're limited to its functionality.

**Library**

There is no explicit library mentioned in the benchmark definition. However, the `Array.isArray()` method is a built-in JavaScript function that comes with the language itself. No external libraries are required to use this feature.

**Special JS Features or Syntax**

The benchmark utilizes several modern JavaScript features:

*   **Optional Chaining (`?.`):** This syntax allows you to access properties or call methods on an object without directly referencing the value of a property, thus avoiding potential null pointer exceptions. It's used in both `myIsArray` and `array?.length`.
*   **Template Literals:** The JSON format uses template literals to create nicely formatted code blocks.

**Other Alternatives**

Some alternative approaches could be:

1.  Using `instanceof`: Instead of `Array.isArray()`, you can use the `instanceof` operator to check if an object is an instance of `Array`. However, this approach has a different syntax and might not be as readable or efficient.
2.  Implementing a custom check: You could write a simple function that checks whether an object has a `.length` property greater than 0. This would have similar performance characteristics to the built-in `Array.isArray()` method but with less elegance.

Keep in mind that these alternatives might change the readability and maintainability of your code, so consider them on a case-by-case basis.

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/116.0.0.0 Safari/537.36

Browser/OS: Chrome 116 on Windows

View result in a separate tab

Test name	Executions per second
Check Array.isArray([])	19687308.0 Ops/sec
Check object?.length	20369428.0 Ops/sec
Check Array.isArray(null)	20831430.0 Ops/sec
Check null?.length	20672322.0 Ops/sec

Related benchmarks:

isArray vs optional length 2 (version: 0)

Array.isArray vs array?.length > 0

Comparing performance of: Check Array.isArray([]) vs Check object?.length vs Check Array.isArray(null) vs Check null?.length

Created: one year ago by: Guest

Jump to the latest result

Check Array.isArray([])

Check object?.length

Check Array.isArray(null)

Check null?.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):