Introduction

This tutorial will guide you on how to create classes and objects in TypeScript. TypeScript, a statically typed superset of JavaScript, introduces the concept of types and classes, making it easier to structure your code in an object-oriented manner.

By the end of this tutorial, you will be able to:

• Define a class in TypeScript.
• Instantiate objects from the class.
• Add properties and methods to the class.

Prerequisites: Basic understanding of JavaScript and TypeScript syntax would be helpful, but not necessary as we will cover the basics.

Step-by-Step Guide

1. Defining a Class

In TypeScript, a class is defined using the keyword class followed by the name of the class. The class name is typically capitalized.

class MyClass { }

2. Class Properties

Inside the class, you can define properties (variables associated with the class). These properties will hold the state of the objects.

class MyClass {
    property1: string;
    property2: number;
}

3. Class Methods

Methods (functions associated with the class) can be defined inside the class. These methods can access the class properties and perform actions.

class MyClass {
    property1: string;
    property2: number;

    myMethod() {
        // actions here
    }
}

4. Creating Objects

You can create an object (instance of a class) using the new keyword followed by the class name and parentheses.

let myObject = new MyClass();

Code Examples

Here are some examples of classes and objects in TypeScript.

Example 1

Let's create a Person class with properties name and age, and a method introduce.

class Person {
    name: string;
    age: number;

    introduce() {
        console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
    }
}

let bob = new Person();
bob.name = "Bob";
bob.age = 25;
bob.introduce(); // Outputs: "Hello, my name is Bob and I am 25 years old."

Example 2

Let's add a constructor to our Person class. The constructor is a special method that is called when an object is created.

class Person {
    name: string;
    age: number;

    constructor(name: string, age: number) {
        this.name = name;
        this.age = age;
    }

    introduce() {
        console.log(`Hello, my name is ${this.name} and I am ${this.age} years old.`);
    }
}

let alice = new Person("Alice", 30);
alice.introduce(); // Outputs: "Hello, my name is Alice and I am 30 years old."

Summary

In this tutorial, you learned how to define a class in TypeScript, create objects from the class, and define properties and methods for the class. You also saw how to use a constructor to initialize the properties.

Next, you could learn about inheritance and interfaces in TypeScript, which will allow you to create more complex class structures.

Additional resources:
- TypeScript Handbook - Classes
- TypeScript for Beginners - Classes

Practice Exercises

1. Create a Car class with properties brand, model, and year. Add a method displayCarInfo that outputs the car's information.

2. Enhance the Car class by adding a constructor that initializes the brand, model, and year properties.

3. Create a Student class with properties name, age, and grade. Add a method promote that increases the grade by one.

Solutions and explanations will be provided upon request.