Interfaces allow you to construct the shape of certain implementation. Interfaces should not really be a new concept to you considering your background in .NET, and in TypeScript it is very much the same.
Interfaces are defined using the keyword interface, as follows:
enum Operand { Sum, Subtract, Multiply, Divide}interface Calculable { left: number; right: number; operand: Operand;}
Furthermore, interfaces support optional members and read-only properties, too:
interface Calculable { readonly left: number; readonly right: number; operand?: Operand;}
In the preceding example, the Calculable interface has two readonly properties, left and right, as well as an optional operand property. Read-only declarations can only be set when ...
