TypeScript - Method Overriding - Tutorial Kart

TypeScript ? Method Overriding

TypeScript ? Method Overriding

Method Overriding is a process of overthrowing a method of super class by method of same name and parameters in sub class.

Method Overriding is useful when sub class wants to modify the behavior of super class for certain tasks.

Example

Following is a simple example of method overriding where eat() method of Student class overrides the eat() method of Person class.

class Person{ name:string

eat():void{ console.log(this.name+" eats when hungry.")

} }

class Student extends Person{ // variables rollnumber:number;

// constructors constructor(rollnumber:number, name1:string){

super(); // calling Parent's constructor this.rollnumber = rollnumber this.name = name1 }

// functions displayInformation():void{

console.log("Name : "+this.name+", Roll Number : "+this.rollnumber) }

// overriding super class method eat():void{

console.log(this.name+" eats during break.") } }

var student1 = new Student(2, "Rohit")

student1.displayInformation() student1.eat()

When the above .ts program is compiled to .js file.

var __extends = (this && this.__extends) || (function () { var extendStatics = Object.setPrototypeOf || ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) || function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; }; return function (d, b) { extendStatics(d, b); function __() { this.constructor = d; } d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __()); };

})(); var Person = /** @class */ (function () {

function Person() { } Person.prototype.eat = function () {

console.log(this.name + " eats when hungry."); }; return Person; }()); var Student = /** @class */ (function (_super) { __extends(Student, _super); // constructors function Student(rollnumber, name1) {

var _this = _super.call(this) || this; _this.rollnumber = rollnumber; _this.name = name1; return _this; } // functions Student.prototype.displayInformation = function () { console.log("Name : " + this.name + ", Roll Number : " + this.rollnumber); }; // overriding super class method Student.prototype.eat = function () { console.log(this.name + " eats during break."); }; return Student; }(Person)); var student1 = new Student(2, "Rohit"); student1.displayInformation(); student1.eat();

You can execute .js file using a try javascript online editor by copying the javascript code to the code editor,

Name : Rohit, Roll Number : 2 VM73:35 Rohit eats during break.

Call Super Class Methods from Sub-Class

Immediate super class methods could be called from sub class using super keyword.

eat():void{ super.eat() console.log(this.name+" eats during break.")

}

Replace this method with that of in Student class and run the program.

The eat() method in Person class is executed for super.eat().

Conclusion

In this TypeScript Tutorial, we have learnt to override the behavior of parent classes using Method Overriding with the help of Example TypeScript program.

TypeScript

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TypeScript Object Oriented Concepts

TypeScript Class TypeScript Inheritance TypeScript Method Overriding TypeScript Interface

TypeScript String Operations

TypeScript String Length TypeScript String Split

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