Javascript Classes

Javascript Class Definition

class Car {  constructor(brand) {    this.brand = brand;  }  present() {    return 'I have a ' + this.brand;  }}let myCar = new Car('Ford');document.write(myCar.present());

Private Class Variables in Javascript

Private class variables in JavaScript allow encapsulation, hiding the implementation details and restricting access from outside the class. They are marked by a # symbol in front of the variable name in the class definition.

class User {  #password;  constructor(name, password) {    this.name = name;    this.#password = password;  }}let user = new User('John', '12345');

Use Class Property in Javascript

Class properties allow you to define properties directly within the class. These can often simplify the constructor method by reducing the need to define properties within it.

class Rectangle {  width = 10;  height = 20;  constructor(length, breadth) {    this.length = length;    this.breadth = breadth;  }}

Class Methods in Javascript

Class methods in JavaScript are functions that belong to the class directly. They provide behaviors for class instances and are defined using the class’s function definition syntax.

class Circle {  constructor(radius) {    this.radius = radius;  }  getArea() {    return Math.PI * this.radius * this.radius;  }  getCircumference() {    return 2 * Math.PI * this.radius;  }}

Javascript Class Inheritance Explained

Inheritance is a fundamental concept in object-oriented programming that allows a class to inherit properties and methods from another class. In JavaScript, this is implemented using the concept of prototypical inheritance.

Basic Concepts of Inheritance

The basic concept of inheritance involves creating a parent class and extending it by a child class. Inheritance allows you to build on existing functionality, making your programming experience more efficient.

• Parent Class: This is the class that serves as a foundation and provides properties and methods to child classes.
• Child Class: This class inherits from the parent class and can have its unique properties and methods.

class Vehicle {  constructor(brand) {    this.brand = brand;  }  drive() {    return 'Driving a ' + this.brand;  }}class Car extends Vehicle {  constructor(brand, model) {    super(brand);    this.model = model;  }  displayInfo() {    return this.drive() + ', model ' + this.model;  }}

Implementing Inheritance in Javascript Classes

To implement inheritance in JavaScript classes, you can use the extends keyword. This keyword sets up the prototype chain, allowing the child class to access the properties and methods of the parent class.

class Animal {  speak() {    return 'Animal speaks';  }}class Dog extends Animal {  speak() {    return 'Woof!';  }}

Examples of Javascript Class Inheritance

Various examples can demonstrate how class inheritance works in JavaScript. By creating a hierarchy of classes, you can promote code reuse and maintain a clear structure:

• Consider a Shape class followed by specific shapes like Circle and Square.
• A general Employee class extended by Manager and Developer classes.

class Shape {  constructor() {    this.type = 'shape';  }}class Circle extends Shape {  constructor(radius) {    super();    this.radius = radius;  }  getArea() {    return Math.PI * this.radius * this.radius;  }}

Practical Applications of Javascript Classes

Javascript Classes are essential for building scalable and efficient applications. They are primarily used to create objects and organize code effectively. In modern JavaScript, classes provide a structured approach to managing and implementing complex programming requirements.

Creating Objects with Javascript Classes

One of the primary uses of Javascript Classes is to create objects, which are fundamental components of object-oriented programming. Classes serve as blueprints for objects, encapsulating data and behavior in a single location. To create an object, you instantiate a class using the new keyword.

• Define the class with properties and methods.
• Use the new keyword to create an object instance.
• Access and manipulate properties using methods.

class Book {  constructor(title, author) {    this.title = title;    this.author = author;  }  describe() {    return `Title: ${this.title}, Author: ${this.author}`;  }}let book1 = new Book('1984', 'George Orwell');document.write(book1.describe());

Integrating Javascript Classes in Projects

Integrating Javascript Classes into your projects can streamline development and maintenance processes. By using classes, you can group related functionalities, improve readability, and enable easier collaboration among team members. Classes also facilitate code reuse, making your project modular and manageable.

class User {  constructor(username, email) {    this.username = username;    this.email = email;  }  login() {    console.log(`${this.username} has logged in.`);  }  logout() {    console.log(`${this.username} has logged out.`);  }}let user1 = new User('johnDoe', 'john@example.com');user1.login();

Common Mistakes and Best Practices with Javascript Classes

When working with Javascript Classes, it's essential to be aware of common mistakes and best practices. Proper understanding can help prevent errors and enhance code functionality. Following structured guidelines ensures that you utilize JavaScript classes effectively in your projects.

Avoiding Errors with Private Class Variables

Using private class variables can often lead to errors if not implemented correctly. These variables are intended to restrict access and ensure data encapsulation within a class. Errors can occur if you attempt to access or modify them outside the class scope.

• Syntax Error: Forgetting the # can lead to syntax errors or unintended public properties.
• Access Errors: Attempting to access these variables directly from outside the class will result in errors.

class Account {  #balance;  constructor(initialBalance) {    this.#balance = initialBalance;  }  deposit(amount) {    this.#balance += amount;  }}let account = new Account(100);// Correct the mistake of trying to access private variable like:// console.log(account.#balance); // This will throw an error

Best Practices for Using Class Methods

To make the most efficient use of class methods in JavaScript, adhere to certain best practices. These practices can improve performance, readability, and scalability of your code.

• Encapsulation: Keep methods focused and limit the scope of changes they perform.
• Readability: Choose self-explanatory function names to describe their purpose.
• Documentation: Use documentation comments to explain complex logic within methods.

class Calculator {  add(a, b) {    return a + b;  }  subtract(a, b) {    return a - b;  }}

Efficient Use of Class Property in Javascript

Efficient use of class properties can significantly enhance both performance and reliability of JavaScript applications. Proper assignment and initialization of properties help avoid runtime errors.

class Person {  name;  #age;  constructor(name, age) {    this.name = name;    this.#age = age;  }  getAge() {    return this.#age;  }}