JavaScript typeof Operator

The typeof operator returns the type of variables and values. For example,

const a = 9;

console.log(typeof a); // number
console.log(typeof '9'); // string
console.log(typeof false); // boolean

Syntax of typeof Operator

The syntax of typeof operator is:

typeof operand

Here, operand is a variable name or a value.

typeof Types

The possible types that are available in JavaScript that typeof operator returns are:

Example 1: typeof for String

const str1 = 'Peter';
console.log(typeof str1); // string

const str2 = '3';
console.log(typeof str2); // string

const str3 = 'true';
console.log(typeof str3); // string

Example 2: typeof for Number

const number1 = 3;
console.log(typeof number1); // number

const number2 = 3.433;
console.log(typeof number2); // number

const number3 = 3e5
console.log(typeof number3); // number

const number4 = 3/0;
console.log(typeof number4); // number

Example 3: typeof for BigInt

const bigInt1 = 900719925124740998n;
console.log(typeof bigInt1); // bigint

const bigInt2 = 1n;
console.log(typeof bigInt2); // bigint

Example 4: typeof for Boolean

const boolean1 = true;
console.log(typeof boolean1); // boolean

const boolean2 = false;
console.log(typeof boolean2); // boolean

Example 5: typeof for Undefined

let variableName1;
console.log(typeof variableName1); // undefined

let variableName2 = undefined;
console.log(typeof variableName2); // undefined

Example 6: typeof for null

const name = null;
console.log(typeof name); // object

console.log(typeof null); // object

Example 7: typeof for Symbol

const symbol1 = Symbol();
console.log(typeof symbol1); // symbol

const symbol2 = Symbol('hello');
console.log(typeof symbol2); // symbol

Example 8: typeof for Object

let obj1 = {};
console.log(typeof obj1); // object

let obj2 = new String();
console.log(typeof obj2); // object

let obj3 = [1, 3, 5, 8];
console.log(typeof obj3); // object

Example 9: typeof for Function

let func = function () {};
console.log(typeof func); // function

// constructor function
console.log(typeof String); // function

console.log(typeof Number); // function

console.log(typeof Boolean); // function

Uses of typeof Operator

• The typeof operator can be used to check the type of a variable at a particular point. For example,

let count = 4;
console.log(typeof count);

count = true;
console.log(typeof count);

• You can perform different actions for different types of data. For example,

let count = 4;
if(typeof count === 'number') {
    // perform some action
}
else if (typeof count = 'boolean') {
      // perform another action
}