Benchmark: Array isArray vs instanceof 2

Script Preparation code:

var test = [1,2,3,4];
var c;

Tests:

Instanceof
if ([1,2,3,4] instanceof Array) { c++; }
isArray
if (Array.isArray([1,2,3,4])) { c++; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Instanceof
isArray

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Measuring JavaScript performance is crucial for creating efficient and scalable applications. Let's break down the provided benchmark definitions to understand what's being tested.

**Benchmark Overview**

The benchmark measures the performance difference between two approaches:

1. `instanceof` (using the `Array` constructor)
2. `Array.isArray()` (a modern method introduced in ECMAScript 2015)

Both methods check if a given value is an array. The test aims to determine which approach is faster and more efficient.

**Options Compared**

The two options being compared are:

1. **Using `instanceof` with the `Array` constructor**: This method checks if the object passed in the parentheses has an instance of the `Array` class, which returns a boolean value indicating whether it's an array or not.
2. **Using `Array.isArray()`**: Introduced in ECMAScript 2015, this method provides a more concise and readable way to check if a given value is an array.

**Pros and Cons**

1. **Using `instanceof` with the `Array` constructor**:
	* Pros: More explicit and clear, allowing developers to easily understand the intent behind the code.
	* Cons: May be slower due to the overhead of the `instanceof` operator and the need to check for a specific class.
2. **Using `Array.isArray()`**:
	* Pros: More concise, readable, and efficient, as it uses an optimized method specifically designed for array checks.
	* Cons: Requires ECMAScript 2015 support or later, making older browsers incompatible.

**Other Considerations**

When choosing between these two approaches:

* **Code readability**: If code readability is more important than performance, `Array.isArray()` might be a better choice.
* **Compatibility**: When targeting older browsers that don't support `Array.isArray()`, the `instanceof` method may be necessary.

**Library and Special JS Features**

There are no libraries used in this benchmark. However, note that ECMAScript 2015 is a standard language feature introduced by the European Computer Manufacturers Association (ECMA).

**Special JS Feature**

The test case uses a special JavaScript feature called "preamble code" (in this case, `var c;`) to define variables and control flow before running the actual benchmark. This approach allows for more flexibility in crafting custom benchmarks.

Overall, this benchmark provides valuable insight into the performance differences between two commonly used methods for checking if a value is an array in JavaScript.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.41 Safari/537.36

Browser/OS: Chrome 101 on Linux

View result in a separate tab

Test name	Executions per second
Instanceof	2392594.2 Ops/sec
isArray	2340730.2 Ops/sec

Related benchmarks:

Array isArray vs instanceof 2 (version: 0)

Comparing performance of: Instanceof vs isArray

Created: 5 years ago by: Guest

Jump to the latest result

Instanceof

isArray

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):