Skip to main content
HashnodeUntitled Publication

Command Palette

Search for a command to run...

🔥 How to check if something is an array in JavaScript

Published
•1 min read
D
Dom Habersack

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
#javascript

Comments (2)

Join the discussion
P
Purvi Barot5y ago

In modern browsers you can do:

Array.isArray(obj)

For backward compatibility you can add the following:

// only implement if no native implementation is available
if (typeof Array.isArray === 'undefined') {
  Array.isArray = function(obj) {
    return Object.prototype.toString.call(obj) === '[object Array]';
  }
};
P
Purvi Barot5y ago

In modern browsers you can do:

Array.isArray(obj)

For backward compatibility you can add the following:

// only implement if no native implementation is available
if (typeof Array.isArray === 'undefined') {
  Array.isArray = function(obj) {
    return Object.prototype.toString.call(obj) === '[object Array]';
  }
};

More from this blog

Untitled Publication

8 posts