Benchmark: Array.isArray vs constructor f

Script Preparation code:

var a = []
var d = Array.isArray

Tests:

isArray
d(a)
constructor
a.constructor === Array

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
isArray
constructor

Fastest: N/A

Slowest: N/A

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

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Let's break down the provided benchmark definition and test cases.

**What is being tested?**

The benchmark tests two approaches to check if an array is an instance of the Array constructor:

1. `Array.isArray(a)`: This checks if the `a` variable, which is initialized as an empty array `[]`, is an array using the `Array.isArray()` function.
2. `a.constructor === Array`: This checks if the constructor of the `a` variable (i.e., its prototype chain) equals the `Array` constructor.

**Options compared**

The two options being compared are:

* Using the `Array.isArray()` function
* Using the constructor equality operator (`===`) to check if a value is an instance of a specific constructor

**Pros and Cons of each approach:**

1. **Using `Array.isArray()`**:
	* Pros:
		+ More explicit and readable way to check if a value is an array.
		+ Fewer dependencies on the underlying implementation.
	* Cons:
		+ May be slower than using the constructor equality operator, as it involves a function call and potential caching mechanisms.
2. **Using `constructor === Array`**:
	* Pros:
		+ Often faster and more efficient than using `Array.isArray()`, as it directly checks the prototype chain of an object.
	* Cons:
		+ Less readable and more prone to errors, as it relies on a subtle property of objects that might not be immediately apparent.

**Other considerations:**

* The use of `Array.isArray()` is generally recommended for its readability and maintainability. However, in performance-critical code or edge cases, the constructor equality operator might be preferred.
* It's worth noting that the behavior of `Array.isArray()` can vary depending on the implementation of JavaScript engines (e.g., V8 in Chrome). The test results from MeasureThat.net may not reflect real-world usage.

**Library and special JS feature:**

There is no specific library mentioned in the benchmark definition. However, it's worth noting that the use of `Array.isArray()` relies on a property of arrays that is defined by the ECMAScript standard.

**Special JS feature:**

No special JavaScript features or syntax are used in this benchmark. The focus is solely on comparing two approaches to check if an array is an instance of the Array constructor.

Related benchmarks:

Array.isArray vs constructor f (version: 0)

Comparing performance of: isArray vs constructor

Created: 3 years ago by: Guest

Jump to the latest result

isArray

constructor

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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