Benchmark: Array type test comparison

Script Preparation code:

var types = {
  array: [1,2,3],
  number: 123,
  string: '123',
  map: new Map([[1,1],[2,2],[3,3]]),
  set: new Set([1,2,3]),
  buffer: new ArrayBuffer([1,2,3]),
  boolean: true,
  arrow: () => {},
  function: function () {},
  object: {},
  u8: new Uint8Array(),
  u16: new Uint16Array(),
  u32: new Uint32Array(),
  i8: new Int8Array(),
  i16: new Int16Array(),
  i32: new Int32Array()
}

Tests:

instanceof
const t1 = types.array instanceof Array const t2 = types.object instanceof Array
isArray
const t1 = Array.isArray(types.array) const t2 = Array.isArray(types.object)
Symbol.iterator
const t1 = types.array[Symbol.iterator] !== undefined const t2 = types.object[Symbol.iterator] !== undefined

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
isArray
Symbol.iterator

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares different ways to check if an object is an array or not in JavaScript. The test cases cover three approaches:

1. `instanceof`
2. `isArray`
3. `Symbol.iterator`

These methods are used to determine if a value is an array, and the benchmark measures their performance.

**Options Compared**

The benchmark compares the following options:

* `instanceof Array`: This method checks if the object's prototype chain includes the `Array` constructor.
* `Array.isArray()`: This method takes an object as an argument and returns a boolean indicating whether the object is an array or not.
* Checking for the presence of the `Symbol.iterator` property: In JavaScript, arrays have a `Symbol.iterator` property that can be used to iterate over the elements of an array.

**Pros and Cons**

Here's a brief summary of each approach:

* `instanceof Array`:
	+ Pros: Simple and straightforward.
	+ Cons: Can be slower due to the overhead of checking the prototype chain.
* `Array.isArray()`: 
	+ Pros: Fast and efficient, as it directly checks if the object is an array.
	+ Cons: May not work correctly for non-array objects with a numeric index signature (e.g., `Object.values()` returns an array-like object).
* Checking for `Symbol.iterator`:
	+ Pros: Can be faster than `instanceof` or `Array.isArray()` for large arrays, as it only checks for the presence of the property.
	+ Cons: May not work correctly for non-array objects (e.g., `Object()`) and requires additional processing to iterate over the elements.

**Library Usage**

There is no explicit library usage in this benchmark. However, it's worth noting that `Array.isArray()` is a built-in method in JavaScript.

**Special JS Features or Syntax**

This benchmark does not use any special JavaScript features or syntax beyond what's commonly used in modern JavaScript development.

**Alternative Approaches**

Other ways to check if an object is an array include:

* Using the `typeof` operator with the `array` keyword: `typeof obj === 'object' && obj instanceof Array`
* Using a helper function that checks for specific properties (e.g., `Object.keys(obj).length > 0`)

Keep in mind that these approaches may have different performance characteristics and may not be as efficient as using built-in methods like `Array.isArray()`.

Overall, the benchmark provides valuable insights into the performance of different approaches to checking if an object is an array in JavaScript.

Related benchmarks:

Array type test comparison (version: 0)

Comparing performance of: instanceof vs isArray vs Symbol.iterator

Created: 6 years ago by: Registered User

Jump to the latest result

instanceof

isArray

Symbol.iterator

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):