TypeScript Classes

Traditional JavaScript uses functions and prototype-based inheritance to build up reusable components, but this may feel a bit awkward to programmers more comfortable with an object-oriented approach, where classes inherit functionality and objects are built from these classes. Starting with ECMAScript 2015, also known as ECMAScript 6, JavaScript programmers will be able to build their applications using this object-oriented class-based approach. In TypeScript, we allow developers to use these techniques now, and compile them down to JavaScript that works across all major browsers and platforms, without having to wait for the next version of JavaScript.
Classes

Let’s take a look at a simple class-based example:

class Greeter {
greeting: string;
constructor(message: string) {
this.greeting = message;
}
greet() {
return “Hello, ” + this.greeting;
}
}

let greeter = new Greeter(“world”);

The syntax should look familiar if you’ve used C# or Java before. We declare a new class Greeter. This class has three members: a property called greeting, a constructor, and a method greet.

You’ll notice that in the class when we refer to one of the members of the class we prepend this.. This denotes that it’s a member access.

In the last line we construct an instance of the Greeter class using new. This calls into the constructor we defined earlier, creating a new object with the Greeter shape, and running the constructor to initialize it.

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