How to check the type of a variable or object in JavaScript ?

In this article, How to Check the Type of a Variable or Object in JavaScript? In JavaScript, the typeof operator is used to determine the typeof an object or variable. JavaScript, on the other hand, is a dynamically typed (or weakly typed) language. This indicates that a variable can have any type of value. The type of the value assigned to a variable determines the type of the variable.

The typeof operator in JavaScript allows you to determine the type of value or type of value that a variable contains . There is just one operand for the typeof operator (a unary operator), which takes one variable as input. It determines the operand’s type and a string is returned as a result.

Let’s understand the typeof operator using some examples:

Example 1: If a string variable is checked by typeof, the result will be “string”.

Javascript

<script>
  var apple = "apple";
  console.log(typeof apple);
</script>

Output:

"string"

Example 2: When we check the type of a number variable it results in the string “number”.

Javascript

<script>
  var number = 2052021;
  console.log(typeof number);
</script>

Output:

"number"

Example 3: When we check the type of undefined it is “undefined”.

Javascript

<script>
  console.log(typeof undefined);
</script>

Output:

"undefined"

Example 4: The type of special symbol is “string”.

HTML

<script>
  var symbol = "@";
  console.log(typeof symbol);
</script>

Output:

"string"

Example 5: The type of null is “object”.

HTML

<script>
  console.log(typeof null);
</script>

Output:

"object"

Example 6: The type of NaN ( not a number ) returns “number”.

Javascript

<script>
  console.log(typeof NaN);
</script>

Output:

"number"

Example 7: In this example, a new object is created using a new keyword. typeof the variable created as “object”.

Javascript

<script>
  let obj = new String("this is a string")
  console.log(typeof obj);
</script>

Output:

"object"

Example 8: In the below example, a function is created to find the sum of two numbers and is passed on to a variable. type of the function variable is “function”.

Javascript

<script>
  let func_object = function (a, b) {
    return a + b;
  };
  console.log(typeof func_object);
</script>

Output:

"function"