TypeScript - Classes

Classes are a programming property used in Objected Oriented Programming. In TypeScript, you can use a Class with Interface like below;

class Student {
  fullName: string;
  constructor(
    public firstName: string,
    public middleInitial: string,
    public lastName: string
  ) {
    this.fullName = firstName + " " + middleInitial + " " + lastName;
  }
}

interface Person {
  firstName: string;
  lastName: string;
}

function greeter(person: Person) {
  return "Hello, " + person.firstName + " " + person.lastName;
}

let user = new Student("Jane", "M.", "User");

document.body.textContent = greeter(user);

First you declare a class called Student. In its constructor, it takes arguments like firstName, middleInitial, and lastName. The use of public on arguments indicate that you can create properties with that name.

The Person interface, which is the type of an argument for the function greeter, declares the types of firstName and lastName. Thus ensuring the created user object has the types that can be used for the greeter function.