Basic

class Car {
  constructor(name) {
    this.name = name;
  }
  drive() {
    console.log(this.name, 'driving');
  }
}

const toyota = new Car('toyota');
toyota.drive(); // toyota driving

const subaru = new Car('subaru');
subaru.drive(); // subaru driving

Property Initializer

class Counter {
  count = 0;
  increment() {
    this.count++;
  }
}

const counter = new Counter();
console.log(counter.count); // 0

counter.increment();
console.log(counter.count); // 1

Private Properties

class Event {
  #eventName;
  constructor(eventName) {
    this.#eventName = eventName;
  }
  fire() {
    console.log(this.#eventName);
  }
}

const evt = new Event('click');
evt.fire(); // click

evt.#eventName = 'open'; // ERROR: Private field

Static Members

class Square {
  static howManySquares = 0;
  constructor(size) {
    Square.howManySquares++;
    this.size = size;
  }
  area() {
    return this.size * this.size;
  }
}

const unit = new Square(1);
const quad = new Square(4);

console.log(Square.howManySquares); // 2

Getters and Setters

class RangedValue {
  #current;
  constructor({ min, max, value }) {
    this.min = min;
    this.max = max;
    this.#current = value;
  }
  get value() {
    return this.#current;
  }
  set value(newValue) {
    this.#current = Math.max(this.min, Math.min(this.max, newValue));
  }
}

const ranged = new RangedValue({ value: 5, min: 0, max: 10 });
console.log(ranged.value); // 5

ranged.value = 15;
console.log(ranged.value); // 10

Inheritance

class Animal {
  constructor(name) {
    this.name = name;
  }
  eat() {
    console.log('yum yum');
  }
}

const simple = new Animal('Dimple');
console.log(simple.name); // Dimple
simple.eat(); // yum yum

class Bird extends Animal {
  constructor(name, weight) {
    super(name);
    this.weight = weight;
  }
  fly() {
    console.log(this.weight > 3 ? 'Too fat to fly' : '🎤 I believe I can fly 🎤');
  }
}

const bird = new Bird('Polly', 2);

console.log(bird.name); // Polly
bird.eat(); // yum yum

console.log(bird.weight); // 2
bird.fly(); // 🎤 I believe I can fly 🎤

instanceof

class Alpha { }
class Beta { }

const alpha = new Alpha();
const beta = new Beta();

console.log(typeof alpha); // 'object'
console.log(typeof beta); // 'object'

console.log(alpha instanceof Alpha); // true
console.log(alpha instanceof Beta); // false

console.log(beta instanceof Alpha); // false
console.log(beta instanceof Beta); // true

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Professional Modern JavaScript Lessons

JavaScript Classes - Object Oriented Programming

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Basic

Property Initializer

Private Properties

Static Members

Getters and Setters

Inheritance

instanceof

Transcript

Professional Modern JavaScript