Classes (ES6) in JavaScript

1// Class declaration
2class Person {
3    constructor(name, age) {
4        this.name = name;
5        this.age = age;
6    }
7    
8    greet() {
9        return `Hello, I'm ${this.name}`;
10    }
11    
12    getAge() {
13        return this.age;
14    }
15}
16
17let person1 = new Person("Alice", 25);
18console.log(person1.greet());
19console.log("Age:", person1.getAge());
20
21// Class with inheritance
22class Student extends Person {
23    constructor(name, age, grade) {
24        super(name, age);  // Call parent constructor
25        this.grade = grade;
26    }
27    
28    study() {
29        return `${this.name} is studying`;
30    }
31    
32    // Override parent method
33    greet() {
34        return `Hi, I'm ${this.name}, a student`;
35    }
36}
37
38let student1 = new Student("Bob", 20, "A");
39console.log("\nStudent:");
40console.log(student1.greet());
41console.log(student1.study());
42console.log("Grade:", student1.grade);
43
44// Static methods
45class MathUtils {
46    static add(a, b) {
47        return a + b;
48    }
49    
50    static multiply(a, b) {
51        return a * b;
52    }
53}
54
55console.log("\nStatic methods:");
56console.log("Add:", MathUtils.add(5, 3));
57console.log("Multiply:", MathUtils.multiply(5, 3));
58
59// Getters and Setters
60class Circle {
61    constructor(radius) {
62        this._radius = radius;
63    }
64    
65    get radius() {
66        return this._radius;
67    }
68    
69    set radius(value) {
70        if (value > 0) {
71            this._radius = value;
72        } else {
73            throw new Error("Radius must be positive");
74        }
75    }
76    
77    get area() {
78        return Math.PI * this._radius ** 2;
79    }
80}
81
82let circle = new Circle(5);
83console.log("\nCircle:");
84console.log("Radius:", circle.radius);
85console.log("Area:", circle.area.toFixed(2));
86circle.radius = 10;
87console.log("New radius:", circle.radius);
88console.log("New area:", circle.area.toFixed(2));