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Inheritance is an important concept in object-oriented programming. In the classical inheritance, methods from base class get copied into derived class. So let’s understand Inheritance in JavaScript in the following manner:
Inheritance in JavaScript
In JavaScript, inheritance is supported by using a prototype object. Some people call it “Prototypal Inheriatance” and some people call it “Behaviour Delegation”.
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Prototypal Inheritance (Behavior Delegation Pattern)
v1 and v2 are linked to Vehicle.prototype because it’s been created using the new keyword.
Similarly, c1 and c2 are linked to Car.prototype and Car.prototype is linked to Vehicle.prototype.
In JavaScript when we create the object it does not copy the properties or behavior, it creates a link. A similar kind of linkage gets created in case of extending of class as well.
All arrows go in the opposite direction compare to classical non-js inheritance because it’s a behavior delegation link. These links are known as the prototype chain.
This pattern is called Behavior Delegation Pattern which is commonly known as a prototypal inheritance in JavaScript.
Code: Inheritance in JavaScript
!DOCTYPE html>
<html>
<body>
<h1>Demo: Inheritance</h1>
<script>
function Person(firstName, lastName) {
this.FirstName = firstName || "unknown";
this.LastName = lastName || "unknown";
}
Person.prototype.getFullName = function () {
return this.FirstName + " " + this.LastName;
}
function Student(firstName, lastName, schoolName, grade)
{
Person.call(this, firstName, lastName);
this.SchoolName = schoolName || "unknown";
this.Grade = grade || 0;
}
//Student.prototype = Person.prototype;
Student.prototype = new Person();
Student.prototype.constructor = Student;
var std = new Student("James","Bond", "XYZ", 10);
alert(std.getFullName()); // James Bond
alert(std instanceof Student); // true
alert(std instanceof Person); // true
</script>
</body>
</html>
This code will produce the following output.
OUTPUT:
With this, we come to an end of this article. For more information you can refer to the following Blogs:
- Angular Tutorial
- Getting Started With Angular
- Is AngularJS really based on MVC architecture?
- Learn How To Work With Directives In Angular
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