const yyyymmdstr = moment().format("YYYY/MM/DD");

const currentDate = moment().format("YYYY/MM/DD");

const Animal = function (age) { if (!(this instanceof Animal)) { throw new Error("Instantiate Animal with `new`"); } this.age = age; }; Animal.prototype.move = function move() {}; const Mammal = function (age, furColor) { if (!(this instanceof Mammal)) { throw new Error("Instantiate Mammal with `new`"); } Animal.call(this, age); this.furColor = furColor; }; Mammal.prototype = Object.create(Animal.prototype); Mammal.prototype.constructor = Mammal; Mammal.prototype.liveBirth = function liveBirth() {}; const Human = function (age, furColor, languageSpoken) { if (!(this instanceof Human)) { throw new Error("Instantiate Human with `new`"); } Mammal.call(this, age, furColor); this.languageSpoken = languageSpoken; }; Human.prototype = Object.create(Mammal.prototype); Human.prototype.constructor = Human; Human.prototype.speak = function speak() {};

class Animal { constructor(age) { this.age = age; } move() { /* ... */ } } class Mammal extends Animal { constructor(age, furColor) { super(age); this.furColor = furColor; } liveBirth() { /* ... */ } } class Human extends Mammal { constructor(age, furColor, languageSpoken) { super(age, furColor); this.languageSpoken = languageSpoken; } speak() { /* ... */ } }

class Car { constructor(make, model, color) { this.make = make; this.model = model; this.color = color; } setMake(make) { this.make = make; } setModel(model) { this.model = model; } setColor(color) { this.color = color; } save() { console.log(this.make, this.model, this.color); } } const car = new Car("Ford", "F-150", "red"); car.setColor("pink"); car.save();

class Car { constructor(make, model, color) { this.make = make; this.model = model; this.color = color; } setMake(make) { this.make = make; // NOTE: Returning this for chaining return this; } setModel(model) { this.model = model; // NOTE: Returning this for chaining return this; } setColor(color) { this.color = color; // NOTE: Returning this for chaining return this; } save() { console.log(this.make, this.model, this.color); // NOTE: Returning this for chaining return this; } } const car = new Car("Ford", "F-150", "red").setColor("pink").save();

class Employee { constructor(name, email) { this.name = name; this.email = email; } // ... } // Bad because Employees "have" tax data. EmployeeTaxData is not a type of Employee class EmployeeTaxData extends Employee { constructor(ssn, salary) { super(); this.ssn = ssn; this.salary = salary; } // ... }

class EmployeeTaxData { constructor(ssn, salary) { this.ssn = ssn; this.salary = salary; } // ... } class Employee { constructor(name, email) { this.name = name; this.email = email; } setTaxData(ssn, salary) { this.taxData = new EmployeeTaxData(ssn, salary); } // ... }