Like interfaces, classes should not be a new concept to you due to your background in .NET. Classes enable you to define state and behavior in a single unit while promoting encapsulation and reuse. TypeScript supports classes and they look very much like ES6 classes. The following is a simple example of a Calculator class with a single sum function:

class Calculator {
            sum(left: number, right: number): number {
                        return left + right;
            }
}

const calc = new Calculator();
console.log(calc.sum(2,3));