Classes
class Dog {
constructor(name) {
this._name = name;
this._behavior = 0;
}
get name() {
return this._name;
}
get behavior() {
return this._behavior;
}
incrementBehavior() {
this._behavior ++;
}
}
const halley = new Dog('Halley');
console.log(halley.name); // Print name value to console
console.log(halley.behavior); // Print behavior value to console
halley.incrementBehavior(); // Add one to behavior
console.log(halley.name); // Print name value to console
console.log(halley.behavior); // Print behavior value to console
Inheritance Classes
class Animal {
constructor(name) {
this._name = name;
this._behavior = 0;
}
get name() {
return this._name;
}
get behavior() {
return this._behavior;
}
incrementBehavior() {
this._behavior++;
}
}
class Cat extends Animal {
constructor(name, usesLitter) {
super(name);
this._usesLitter = usesLitter;
}
}
const bryceCat = new Cat('Bryce', false);
console.log(bryceCat._name); // output: Bryce
- The extends keyword makes the methods of the animal class available inside the cat class.
- The constructor, called when you create a new Cat object, accepts two arguments, name and usesLitter.
- The super keyword calls the constructor of the parent class. In this case, super(name) passes the name argument of the Cat class to the constructor of the Animal class. When the Animal constructor runs, it sets this._name = name; for new Cat instances.
- _usesLitter is a new property that is unique to the Cat class, so we set it in the Cat constructor.
class HospitalEmployee {
constructor(name) {
this._name = name;
this._remainingVacationDays = 20;
}
get name() {
return this._name;
}
get remainingVacationDays() {
return this._remainingVacationDays;
}
takeVacationDays(daysOff) {
this._remainingVacationDays -= daysOff;
}
static generatePassword(){
const randomNumber = Math.floor(Math.random()*10000);
return randomNumber;
}
}
class Nurse extends HospitalEmployee {
constructor(name, certifications) {
super(name);
this._certifications = certifications;
}
get certifications() {
return this._certifications;
}
addCertification(newCertification) {
this._certifications.push(newCertification);
}
}
class Doctor extends HospitalEmployee{
constructor(name, insurance){
super(name);
this._insurance = insurance;
}
get insurance(){
return this._insurance;
}
}
const nurseOlynyk = new Nurse('Olynyk', ['Trauma','Pediatrics']);
nurseOlynyk.takeVacationDays(5);
console.log(nurseOlynyk.remainingVacationDays);
nurseOlynyk.addCertification('Genetics');
console.log(nurseOlynyk.certifications);
Review: Classes
- Classes are templates for objects.
- Javascript calls a constructor method when we create a new instance of a class.
- Inheritance is when we create a parent class with properties and methods that we can extend to child classes.
- We use the extends keyword to create a subclass.
- The super keyword calls the constructor() of a parent class.
- Static methods are called on the class, but not on instances of the class.
Build a Library
class Media{
constructor(title){
this._title=title;
this._isCheckedOut = false;
this._ratings = [];
}
get title(){
return this._title;
}
get isCheckedOut(){
return this._isCheckedOut;
}
get ratings(){
return this._ratings;
}
set isCheckedOut(input){
this._isCheckedOut = input;
}
toggleCheckOutStatus(){
if(this._isCheckedOut === true){
this._isCheckedOut = false;
}
else{
this._isCheckedOut = true;
}
//this.isCheckedOut = !this.isCheckedOut;
}
getAverageRating(){
const NumOfRating = this._ratings.length;
const reducer = (previous, current) => previous + current;
let ratingSum = this._ratings.reduce(reducer, 0);
//let ratingSum = this.ratings.reduce((accumulator, rating) => accumulator + rating);
return ratingSum/NumOfRating;
}
addRating(rate){
this._ratings.push(rate);
//this.ratings.push(rate);
}
}
class Book extends Media{
constructor(title, author, pages){
super(title);
this._author = author;
this._pages = pages;
}
get author(){
return this._author;
}
get pages(){
return this._pages;
}
}
class Movie extends Media{
constructor(title, director, runTime){
super(title);
this._director = director;
this._runTime = runTime;
}
get director(){
return this._director;
}
get runTime(){
return this._runTime;
}
}
const historyOfEverything = new Book('A Short History of Nearly Everything','Bill Bryson', 544);
historyOfEverything.toggleCheckOutStatus();
console.log(historyOfEverything.isCheckedOut);
historyOfEverything.addRating(4);
historyOfEverything.addRating(5);
historyOfEverything.addRating(5);
console.log(historyOfEverything.ratings);
const avgRating = historyOfEverything.getAverageRating();
console.log(avgRating);
const speed = new Movie('Speed','Jan de Bont',116);
speed.toggleCheckOutStatus();
console.log(speed.isCheckedOut);
speed.addRating(1);
speed.addRating(1);
speed.addRating(5);
console.log(speed.ratings);
console.log(speed.getAverageRating());
School Catalogue
class School{
constructor(name, level, numberOfStudents){
this._name = name;
this._level = level;
this._numberOfStudents = numberOfStudents;
}
get name(){
return this._name;
}
get level(){
return this._level;
}
get numberOfStudents(){
return this._numberOfStudents;
}
set numberOfStudents(newNumberOfStudents){
if(typeof newNumberOfStudents === 'number'){
this._numberOfStudents = newNumberOfStudents;
}else{
console.log('Invalid input: numberOfStudents must be set to a Number.');
}
}
quickFacts(){
console.log(`${this._name} educates ${this._numberOfStudents} students at the ${this._level} school level.`);
}
static pickSubstituteTeacher(substituteTeachers){
const random = Math.floor(Math.random()*(substituteTeachers.length));
return substituteTeachers[random];
}
}
class PrimarySchool extends School{
constructor(name, numberOfStudents, pickupPolicy){
super(name, 'primary', numberOfStudents);
this._pickupPolicy = pickupPolicy;
}
get pickupPolicy(){
return this._pickupPolicy;
}
}
class HighSchool extends School{
constructor(name, numberOfStudents, sportsTeams){
super(name, 'high', numberOfStudents);
this._sportsTeams = sportsTeams;
}
get sportsTeams(){
return this._sportsTeams;
}
}
const lorraineHansbury = new PrimarySchool('Lorraine Hansbury', 514, 'Students must be picked up by a parent, guardian, or a family member over the age of 13.');
lorraineHansbury.quickFacts();
const sub = School.pickSubstituteTeacher(['Jamal Crawford', 'Lou Williams', 'J. R. Smith', 'James Harden', 'Jason Terry', 'Manu Ginobli']);
const alSmith = new HighSchool('Al E. Smith',415, ['Baseball', 'Basketball', 'Volleyball', 'Track and Field']);
console.log(alSmith.sportsTeams);
