Question

How to verify if a variable is an array in Javascript?

Answer 1

It is possible to check if a variable is an array instance using 3 different ways,

1. Array.isArray() method:

   The Array.isArray(value) utility function is used to determine whether value is an array or not. This function returns a true boolean value if the variable is an array and a false value if it is not.

   const numbers = [1, 2, 3];
   const user = { name: "John" };
   Array.isArray(numbers); // true
   Array.isArray(user); //false

2. instanceof operator:

   The instanceof operator is used to check the type of an array at run time. It returns true if the type of a variable is an Array other false for other type.

   const numbers = [1, 2, 3];
   const user = { name: "John" };
   console.log(numbers instanceof Array); // true
   console.log(user instanceof Array); // false

3. Checking constructor type:

   The constructor property of the variable is used to determine whether the variable Array type or not.

   const numbers = [1, 2, 3];
   const user = { name: "John" };
   console.log(numbers.constructor === Array); // true
   console.log(user.constructor === Array); // false