JS Classes

JS Classes

JavaScript classes provide a cleaner syntax for working with objects and prototypes. They are syntactic sugar over prototype-based inheritance.

class User {
  constructor(name) {
    this.name = name;
  }

  greet() {
    return "Hello, " + this.name;
  }
}

const u = new User("Ozan");
console.log(u.greet());

Classes are not hoisted like function declarations.

JS Class Inheritance

Classes can inherit from other classes using extends. Use super() to call the parent constructor.

class Animal {
  constructor(name) {
    this.name = name;
  }

  speak() {
    return "Some sound";
  }
}

class Dog extends Animal {
  speak() {
    return "Woof";
  }
}

const d = new Dog("Max");
console.log(d.name);
console.log(d.speak());

Always call super() in the child constructor before using this.

JS Class Static

Static methods belong to the class itself, not to instances.

class MathHelper {
  static square(n) {
    return n * n;
  }
}

console.log(MathHelper.square(5));
// const m = new MathHelper();
// m.square(5); // Error

Modern features inside classes:

• Private fields: #secret
• Public class fields

class Counter {
  #count = 0;

  inc() {
    this.#count++;
    return this.#count;
  }
}

const c = new Counter();
console.log(c.inc());

Next Step

Continue with JS Asynchronous to understand Promises, async/await, and Fetch.