Checking if something is an array
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