How to check if a JavaScript variable is an array or an object?

Two ways to check if an Array

Using the Object.prototype.toString.call([]).
Using the Array.isArray([]).

Code Samples Below:

const programmingLanguages = ['C#', 'JavaScript', 'Java'];
//old way
console.log(Object.prototype.toString.call(programmingLanguages) === '[object Array]'); //output: true
//new way
console.log(Array.isArray(programmingLanguages)); //output: true

To check if object you can use the typeof operator and check if it is not equal to null. The reason you need to check if not null is because null when passed into the typeof operator returns an “object” result.

const customer = {};
console.log(typeof(customer)); //output: object; 
//but it is better to check if typeof object and not null
console.log(typeof(customer) === "object" && customer !== null); //output: true
const product = null;
//but it is better to check if typeof object and not equal to null
console.log(typeof(product) === "object" && product !==null); //output: false

Jin Necesario6y

$.isArray()

Bidyasagar Mishra7y

let obj ={}; let arr = []; check output of console.log in each variable and you can see that they have different proto. console.log(obj.constructor.prototype.hasOwnProperty('push')); // this will give false because and object don't have a push method where as an array have the push method. console.log(arr.constructor.prototype.hasOwnProperty('push')); // will return true

Neeraj Negi8y

using $.isArray()

Gajendra Jangid8y

Thank you Dang Dang for the post. jQuery, $.isArray() uses Array.isArray() JavaScript method. But it is not supported by older browsers.

Dennis Thomas8y

simply using $.isArray()

Đặng Đang8y

Since a JavaScript Array is an object, typeof operator will return object for an array. So we cannot use that in this case. We can use Array.isArray() in browsers that support ECMAScript 5. Array.isArray(myArray); // returns true But older versions of browsers doesn't support ECMAScript 5. So, you need to write your own function for this. You can check the prototype of the object to search for the word "Array". function isArray(myVar) { return myVar.constructor.toString().indexOf("Array") > -1; } The above function will return true if the parameter is an array.

Dennis Thomas8y

How to check if a JavaScript variable is an array or an object?

7 Answers