Type Operators
Type operators are used to check the type of a variable or object.
The two main type operators in JavaScript are:
typeof Operator
-
Returns a string indicating the type of a variable or value.
Syntax:
typeof operand
Examples:
console.log(typeof 42); // "number"
console.log(typeof 'Hello'); // "string"
console.log(typeof true); // "boolean"
console.log(typeof undefined); // "undefined"
console.log(typeof { name: 'John' }); // "object"
console.log(typeof [1, 2, 3]); // "object"
console.log(typeof function(){}); // "function"
console.log(typeof null); // "object" (this is a known quirk in JS)
instanceof Operator
- Checks whether an object is an instance of a specific class or constructor.
- Returns true or false.
Syntax:
object instanceof constructor
Examples:
let arr = [1, 2, 3];
console.log(arr instanceof Array); // true
console.log(arr instanceof Object); // true
let date = new Date();
console.log(date instanceof Date); // true
console.log(date instanceof Object); // true
function Person(name) {
this.name = name;
}
let p = new Person('John');
console.log(p instanceof Person); // true
console.log(p instanceof Object); // true