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JavaScript Inheritance

The JavaScript inheritance is a mechanism that allows us to create new classes on the basis of already existing classes. It provides flexibility to the child class to reuse the methods and variables of a parent class.

The JavaScript extends keyword is used to create a child class on the basis of a parent class. It facilitates child class to acquire all the properties and behavior of its parent class.

Points to remember

  • It maintains an IS-A relationship.
  • The extends keyword is used in class expressions or class declarations.
  • Using extends keyword, we can acquire all the properties and behavior of the inbuilt object as well as custom classes.
  • We can also use a prototype-based approach to achieve inheritance.

JavaScript extends Example: inbuilt object

In this example, we extends Date object to display today's date.

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Output:

Current date: 31-8-2018

Let's see one more example to display the year value from the given date.

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Output:

Year value: 1947

JavaScript extends Example: Custom class

In this example, we declare sub-class that extends the properties of its parent class.

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Output:

Honda Shine 70000

JavaScript extends Example: a Prototype-based approach

Here, we perform prototype-based inheritance. In this approach, there is no need to use class and extends keywords.

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Output:

Honda Shine 70000
Next TopicJS Polymorphism




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