Classes in JS don’t give JS an OO nature, JS remains Prototypal. Classes introduced in ES6 are mainly syntax sugar.
1"use strict";
2
3// CLASS
4class User{
5 // Constructor
6 // takes any values/attr you want to set
7 constructor(username, email, password) {
8 this.username = username // Whatever username we passed in is now this Class's (instance) username
9 this.email = email
10 this.password = password
11 }
12
13 static countUsers () {
14 console.info('There are 50 users')
15 }
16
17 // Methods
18 register() {
19 console.log(`${this.username} is now registered`)
20 }
21}
22
23// Instantiate the class
24let Bob = new User('bob', 'bob@bobby.com', '123supersecretpass')
25
26// Call a method
27Bob.register() // bob is now registered
28
29// INHERITANCE
30class Memeber extends User {
31 constructor(username, email, password, memberPackage) {
32 super(username, email, password)
33 this.package = memberPackage
34 }
35
36 getPackage() {
37 console.info(`${this.username} is subscribed to the ${this.package} package`)
38 }
39
40}
41let mike = new Member('mike', 'mike@email.com', 'pass123', 'Standard')
42
43mike.register() // mike is now registereds
44mike.getPackage() // mike is subscribed to the Standard package
Constructors are methods that’ll run when your class is instantiated. They can take parameters. You can then set these params (passed in values) and assign them to class properties.
Methods are functions that belong to a class. You can call them on an instance of a class, like so:
1Bob.register() // bob is now registereds
You can also have static methods. Whatever. Static methods can be called without having to instantiate a class, like this:
1User.countUsers() // There are 50 users
You can extend existing classes to create new classes. super constructor calls (functions etc.) on theconstructor in the parent class. super needs to be called before you can use the this keyword.
1class Member extends User {}
You should create a class whenever you have code that needs to be self-aware or keep something in memory. Whatever that means.