🔥 How to check if something is an array in JavaScript

Internally, there is no type called “array” in JavaScript. When used on an array, typeof returns "object" instead.

To check if something is an array, use Array.isArray() instead.

// `typeof` an array returns “object” because JS has no type called “array”.
typeof ['a', 'b', 'c']                     // ⇒ "object"

// The array is treated like this equivalent object.
typeof { 0: 'a', 1: 'b', 2: 'c' }          // ⇒ "object"

// Use `Array.isArray` instead of `typeof` to test if something is an array.
Array.isArray(['a', 'b', 'c'])             // ⇒ true
Array.isArray({ 0: 'a', 1: 'b', 2: 'c' })  // ⇒ false

Comments

[Eliabe França]

I've always used instaceof

[Brandon Weaver]

This is more readable in my opinion.
[0] instanceof Array; // true

[Dom Habersack]

That is a decent alternative. It could cause issues when working with multiple frames, because each context has its own Array object:

developer.mozilla.org/en-US/docs/W...

When working with iframes, Array.isArray() gives you more accurate results. When working with a single context, instanceof is fine.

[Seye Olajuyin]

I had no idea this exists. Thank you!