Observer Pattern

function Observable() {
  this.observers = [];
}

Observable.prototype = {
  subscribe(fn) {
    this.observers.push(fn);
  },
  unsubscribe(fn) {
    this.observers = this.observers.filter((observer) => observer !== fn);
  },
  notify() {
    this.observers.forEach((observer) => {
      if (typeof observer === "function") {
        observer();
      }
    });
  },
};

function changeName() {
  console.log("change name is called");
}

function changeAge() {
  console.log("change age is called");
}

const observe = new Observable();
observe.subscribe(changeAge);
observe.subscribe(changeName);

observe.notify();
// change age is called
// change name is called

class Observable {
  constructor() {
    this.observers = [];
  }
  subscribe(fn) {
    this.observers.push(fn);
  }
  unsubscribe(fn) {
    this.observers = this.observers.filter((observer) => observer !== fn);
  }
  notify() {
    this.observers.forEach((observer) => {
      if (typeof observer === "function") {
        observer();
      }
    });
  }
}

function changeName() {
  console.log("change name is called");
}

function changeAge() {
  console.log("change age is called");
}

const observe = new Observable();
observe.subscribe(changeAge);
observe.subscribe(changeName);

observe.notify();
// change age is called
// change name is called