Exploring Constructors in TypeScript Classes

Welcome to the OOP station! Today, we're going to dive into constructors in TypeScript classes. Constructors play an essential role in creating and initializing objects. Picture a constructor as a blueprint — it details the components necessary for creating each object.

Just like JavaScript, if you don't provide a constructor in your TypeScript class, a default one will be supplied. Imagine this scenario as being given a blank blueprint sheet ready for you to customize!

Let's create our first Car object using the new keyword:

let myCar = new Car("Toyota", "Corolla", "red");
// Prints a message from the constructor:
// Instantiated a Car instance with brand=Toyota, model=Corolla, color=red

myCar is a Car object, representing a red Toyota Corolla. This object has properties defined by the constructor!

Although a TypeScript class can host numerous methods, it is bound by one condition — it can only accommodate a single constructor. If we attempt to declare more than one constructor, TypeScript will raise a SyntaxError.

In instances where no explicit constructor is defined, TypeScript provides a default one: constructor() {}.

Furthermore, we can assign default values to parameters as shown below:

class Car {
  brand: string;
  model: string;
  color: string;

  // 'color' has a default value of "white"
  constructor(brand: string, model: string, color: string = "white") {
    this.brand = brand;
    this.model = model;
    this.color = color;
  }
}