Benchmark: Array isArray vs instanceof vs isEqual vs isLessThan2223

Script Preparation code:

var test = [[1],2,3,4];
var test2 = [-1, 2, 3, 4];
var test3 = ['a', 2, 3, 4];
var c;

Tests:

Instanceof
if (test[0] instanceof Array) { c++; }
isArray
if (Array.isArray(test[0])) { c++; }
isEqual
if (test3[0] === 'a') { c++; }
isLessThan
if(test2[0] < 0) { c++; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Instanceof
isArray
isEqual
isLessThan

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36

Browser/OS: Chrome 83 on Mac OS X 10.15.5

View result in a separate tab

Test name	Executions per second
Instanceof	1700500.9 Ops/sec
isArray	1762588.8 Ops/sec
isEqual	2823379.5 Ops/sec
isLessThan	2355408.8 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared, and the pros and cons of each approach.

**Benchmark Overview**

The benchmark tests four different methods to check if a value is an array:

1. `Array.isArray()`
2. `instanceof Array` (a built-in JavaScript method)
3. `isEqual()` (not a standard JavaScript method, but rather a custom function being tested in this benchmark)
4. `isLessThan()` (not a standard JavaScript method, but rather a custom function being tested in this benchmark)

**Library Used**

In two of the test cases (` isArray` and `Instanceof`), the built-in `Array.isArray()` function is used. This function checks if an object is an array or not.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntax being tested in this benchmark. However, it's worth noting that `instanceof Array` requires an instance of a class (in this case, the `Array` class) to be checked against. The custom functions `isEqual()` and `isLessThan()` are not standard JavaScript methods and are only used for testing purposes.

**Comparison of Methods**

The comparison of these four methods can be broken down as follows:

1. **Speed**: In general, `Array.isArray()` is likely to be the fastest method because it's a built-in function that can take advantage of native optimizations. However, in this benchmark, the results are not conclusive, and there may be variations depending on specific browser implementations or JavaScript engines.
2. **Readability**: Some developers might prefer `instanceof Array` over `Array.isArray()` for readability reasons, as it explicitly checks if a value is an instance of the `Array` class.
3. **Flexibility**: Both `Array.isArray()` and `instanceof Array` can handle arrays with arbitrary elements, but `instanceof Array` may return true for non-array objects that inherit from `Array`, which might be considered a bug.

**Pros and Cons**

Here's a brief pros and cons summary for each method:

* **Array.isArray()**
	+ Pros: Fast, widely supported, and well-maintained.
	+ Cons: May not work correctly for certain types of objects (e.g., `Set` or `Map`).
* **instanceof Array**
	+ Pros: Explicitly checks if a value is an instance of the `Array` class, which can be beneficial for readability.
	+ Cons: May return true for non-array objects that inherit from `Array`, potentially leading to bugs.

**Other Alternatives**

There are other alternatives for checking if a value is an array, such as:

* Using a library like Lodash's `isArray()` function
* Implementing a custom function using recursion or iteration
* Using a regex pattern to match arrays (not recommended due to performance and potential issues)

It's worth noting that the choice of method ultimately depends on the specific use case, personal preference, and performance requirements.

Related benchmarks:

Array isArray vs instanceof vs isEqual vs isLessThan2223 (version: 0)

Comparing performance of: Instanceof vs isArray vs isEqual vs isLessThan

Created: 4 years ago by: Guest

Jump to the latest result

Instanceof

isArray

isEqual

isLessThan

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):