JavaScript OOP

Section 1: Lab: OOP Concepts and Setting Up Tools

• Why write object-oriented code, its benefits and limits, and how it differs from procedural code
• Thinking in objects and separating each class's responsibilities
• Install the Node.js LTS release, VS Code and ESLint
• Organise the project with ES modules and run tests with node --test
• Lab: a starter project used in every lab

Section 2: Objects, Prototypes and this

• Object literals, methods and shorthand
• Constructor functions and how new works
• The prototype chain, Object.create and Object.getPrototypeOf
• The value of this in methods, callbacks and arrow functions
• Lab: build a product object in three ways and compare them

Section 3: Lab: Classes and Objects

• Class declarations, constructors, fields and methods
• Static fields, static methods and static initialisation blocks
• Getters and setters that validate values before storing them
• How classes work on top of prototypes
• Lab: customer account and order classes

Section 4: Encapsulation

• Encapsulate data with private fields and private methods
• Check that an object belongs to a class with #field in obj
• Closures and the module pattern as another way to hide data
• Object.freeze and designing immutable objects
• Lab: a wallet class that stops the balance being changed directly

Section 5: Abstraction

• Design a class's public API so it is easy to use and hides the details
• The abstract class idea in JavaScript, which has no abstract keyword
• Force subclasses to implement methods with new.target and thrown errors
• Duck typing and describing object contracts with JSDoc
• Lab: a base class for several payment methods

Section 6: Lab: Inheritance

• Inherit with extends and call the parent class with super
• Method overriding and extending existing methods
• Extend built-ins such as Error to create custom errors
• instanceof and different kinds of class relationship
• Lab: an employee hierarchy with salary calculation

Section 7: Polymorphism

• What polymorphism is and how it reduces if-else chains
• Overriding versus overloading, which JavaScript does not support directly
• Make objects work with the language through Symbol.iterator and toString
• Use many kinds of object through one interface
• Lab: a shipping cost calculator with several methods

Section 8: Composition and Mixins

• The problems with deep inheritance
• Composition over inheritance and building objects from smaller parts
• Mixins for adding capabilities to several classes
• Dependency injection so parts can be swapped and tested easily
• Lab: turn a class hierarchy into composition

Section 9: The SOLID Principles and Class Diagrams

• Single responsibility and open/closed
• Liskov substitution, interface segregation and dependency inversion
• Read and write UML class diagrams
• Create diagrams from code with Mermaid
• Lab: analyse code that breaks SOLID and redesign it

Section 10: Lab: OOP with TypeScript

• Why teams use TypeScript for object-oriented code
• Interfaces and implements
• Abstract classes, abstract methods and access modifiers
• Parameter properties, readonly and simple generic classes
• Lab: convert the payment system from Section 5 to TypeScript

Section 11: Design Patterns and the Creational Group

• Where design patterns come from, the Gang of Four, and how to choose one
• Singleton, and the ES module alternative
• Factory Method for creating objects based on conditions
• Builder for objects with many settings
• Lab: a factory that creates several notification channels

Section 12: Lab: Structural Patterns

• Composite for tree-shaped data such as menus and categories
• Adapter for connecting to APIs or libraries with a different shape
• Decorator for adding behaviour without changing the original class
• Facade for hiding a complex subsystem
• Proxy with JavaScript's Proxy object

Section 13: Behavioural Patterns

• Observer with EventTarget in the browser and EventEmitter in Node.js
• Strategy for switching calculation methods at run time
• Command for actions that can be undone
• State for objects whose behaviour changes with their status
• Lab: order status handling with State and Observer

Section 14: Lab: Testing and Refactoring Object-oriented Code

• Write unit tests for classes with the Node.js test runner
• Use dependency injection and mocks to test parts in isolation
• Refactor long procedural code into classes step by step under test
• Use an AI assistant to suggest refactorings and verify them with tests
• Lab: refactor an existing discount calculation

Section 15: Workshop: Capstone System Design with OOP and Patterns

• Analyse a booking or order system brief and draw its class diagram
• Choose suitable patterns for each part and justify them
• Write the code to the SOLID principles with tests for the key parts
• Present the work and review the designs together