Introduction to TypeScript for JavaScript Developers

Interfaces

An interface defines the syntax that any entity must adhere to.
Interfaces define properties, methods, and events, which are the members of the interface.
Interfaces contain only the declaration of the members.
It is the responsibility of the deriving class to define the members.
It often helps in providing a standard structure that the deriving classes would follow.
Syntax interface interface_name { }


						interface IPerson { 
							firstName:string, 
							lastName:string, 
							sayHi: ()=>string 
							}



						var customer:IPerson = { 
						firstName:"Tom",
						lastName:"Hanks", 
						sayHi: ():string =>{return "Hi there"} 
						}

Classes

A class in terms of OOP is a blueprint for creating objects.
A class encapsulates data for the object.
Typescript gives built in support for this concept called class.
To create an instance of the class, use the new keyword followed by the class name.

Objects

An object is an instance which contains set of key value pairs.
The values can be scalar values or functions or even array of other objects.

Namespaces

A namespace is a way to logically group related code.
The classes or interfaces which should be accessed outside the namespace should be marked with keyword export.
To access the class or interface in another namespace, the syntax will be namespaceName.className

Modules

A module is designed with the idea to organize code written in TypeScript.
Internal modules came in earlier version of Typescript.
This was used to logically group classes, interfaces, functions into one unit and can be exported in another module.
This logical grouping is named namespace in latest version of TypeScript.