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:
Types | typeof Result |
---|---|
String |
"string" |
Number |
"number" |
BigInt |
"bigint" |
Boolean |
"boolean" |
Object |
"object" |
Symbol |
"symbol" |
undefined |
"undefined" |
null |
"object" |
function | "function" |
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
}