How to Check Object is an Array in JavaScript?

There are two different approaches to check an object is an array or not in JavaScript.

1. Using Array.isArray() Method

The Array.isArray() method determines whether the value passed to this function is an array or not. This method returns true if the argument passed is an array else it returns false.

Syntax

Array.isArray( obj );

function checkObject() {
    const countries = ["India", "USA", "Canada"];
    const checkArrayObj = Array.isArray(countries);

    console.log(checkArrayObj);
}

checkObject();

true

2. Using instanceof Operator

The instanceof operator tests whether an object is an instance of a specific constructor (in this case, Array). This approach is particularly useful because it checks the prototype chain to determine if an object is derived from Array. The instanceof operator checks if the object (array1 or notArray) has Array in its prototype chain. If it does, it returns true, indicating that the object is indeed an array. Otherwise, it returns false.

Syntax

object instanceof Array

const array1 = [1, 2, 3];
const notArray = { name: 'example' };
console.log(array1 instanceof Array);
console.log(notArray instanceof Array); 

true
false