Inheritance in Typescript

In TypeScript, you can inherit a class from another class. Just use the extends keyword to perform inheritance. Consider the following example to understand it better.

class Person {

// properties

firstName: string;

lastName: string;

// construtor

constructor (fName: string, lName: string) {

 // fill the properties

 this.firstName = fName;

 this.lastName = lName;

}

// method

getFullName() {

 return `${firstName} ${lastName}`;

}

}

class Employee extends Person {

// properties

empID: string;

designation: string;

// construtor

constructor (fName: string, lName: string,

eID: string, desig: string) {

 // call the base class constructor

 super(fName, lName);

 // fill the other properties

 this.empID = eID;

 this.designation = desig;

}

// method

getData() {

 return `${empID} - ${firstName} ${lastName}

=> ${designation}`;

}

}

Here the Employee class inherits its base Person by writing class Employee extends Person. In the derived class super(...) is compulsory to call the constructor of the base class. For example, super(fName, lName) in Employee class constructor calls the base class constructor by passing the parameter values fName and lName.

let employee: Employee = new Employee ("Kunal",

                                     "Chowdhury",

                                     "EMP001022",

                                     "Software Engineer"

                                    );

console.log(employee.getData());