Object Oriented Approach - TypeScript - JavaScript's Superset

A Class in terms of OOP is a blueprint for creating objects. It includes: fields, constructor and functions. We use "new" keyword to initialize the class object. Example:

Class in TypeScript

class Student{
    name: string;
}

var newClassObject = new Student();
newClassObject = {
    name: "rajesh";
}

Compiled Class in JavaScript

    var Student = (function () {
        function Student() {
        }
        return Student;
    }());
    var newClassObject = new Student();
    newClassObject = {
        name: "rajesh"
    };

Note: Class in TypeScript can be transferred to JavaScript.

We can define the scope of variable inside classes as public or private. It is important to note that the public or private keywords are only available in TypeScript.

class Student {
 private firstName: string;  //private members
 private lastName: string;
 yearOfBirth: number;    //Public scope by default
 schoolName: string;
 city: string;

    //Constructor            
    constructor(firstName: string, lastName: string, schoolName: string, city: string, yearOfBirth: number) {
            this.firstName = firstName;
         this.lastName = lastName;
         this.yearOfBirth = yearOfBirth;
         this.city = city;
         this.schoolName = schoolName;
     }

    age() {
        return 2017 - this.yearOfBirth;
    }    

    printStudentFullName(): void {
        alert(this.lastName + ',' + this.firstName);
    }
}

Interface helps in detecting error in compile time.

	interface Volume {
		length: number;
		width: number;
		sayHi: () => string;
	}
	//Volume binding object Physics to define all members as specified by interface 
	var Physics: Volume = {
		length: 10,
		width: "ten",
		sayHi: (): string => { return "Hello" }
	}