JavaScript Classes
Introduction
JavaScript Classes
Introduction
JavaScript classes are a powerful feature introduced in ES6, providing a structured approach to object-oriented programming. They offer a blueprint for creating objects with reusable properties and methods, making code more organized and maintainable.
JS Classes
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Defining Classes
Classes are defined using the
classkeyword followed by the class name and curly braces. Inside the curly braces, you define properties and methods.class Vehicle { // Class definition // ... properties and methods } -
Class Properties
Properties are variables that represent the attributes of an object. They are defined within the class body.
class Vehicle { model: string; color: string; year: number; // ... methods } -
Class Methods
Methods are functions defined within a class that perform actions on the object's properties.
class Vehicle { // ... properties startEngine() { console.log('Engine started!'); } } -
Constructor
The
constructormethod is a special method that is called when a new object is created from the class. It initializes the object's properties.class Vehicle { model: string; color: string; year: number; constructor(model: string, color: string, year: number) { this.model = model; this.color = color; this.year = year; } // ... methods }
Inheritance
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Extending Classes
Inheritance allows you to create new classes (child classes) that inherit properties and methods from existing classes (parent classes). This promotes code reuse.
class Car extends Vehicle { // ... additional properties and methods } -
Overriding Methods
Child classes can override methods from the parent class to provide their own implementation. This allows for specialized behavior in child classes.
class Car extends Vehicle { startEngine() { console.log('Car engine started!'); } } -
Using super Keyword
The
superkeyword is used to access the parent class's constructor and methods within the child class.class Car extends Vehicle { constructor(model: string, color: string, year: number, doors: number) { super(model, color, year); this.doors = doors; } // ... methods } -
this and super Use
The
thiskeyword refers to the current instance of the class. Thesuperkeyword refers to the parent class.Do You Know?
Using
super()in the child class constructor is crucial for initializing the inherited properties from the parent class. -
Accessing Private Properties of Parent Class
You can access private properties of the parent class by declaring them using the
#symbol. Then you can use thesuperkeyword to access them.class Vehicle { #brand: string; constructor(brand: string) { this.#brand = brand; } } class Car extends Vehicle { constructor(brand: string, model: string) { super(brand); this.model = model; } getBrand() { return super.#brand; } }Avoid This
Avoid directly accessing private properties of the parent class from outside the child class. This can lead to unexpected behavior and break encapsulation.
Summary
- JavaScript classes provide a structured way to define objects with reusable properties and methods.
- Inheritance allows child classes to inherit properties and methods from parent classes.
- The
superkeyword is used to access parent class's methods and constructors. - Private properties are denoted by the
#symbol and can only be accessed from within the class.
Discussion
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