Inheritance and Implements

A class can extend another class and implement an interface, which is a promise to have certain members.

Exampletypescript

constructor(public name: string) is a shortcut that declares and assigns the property. If a class forgets to deliver the promise:

Exampletypescript

Quick check

What does `implements Speaker` require?

The class must extend SpeakerThe class must have everything Speaker describesNothing; it is a comment

Your turn: write the code

Make Square implement Shape so that area() returns the side squared. Print the area of a square with side 5.

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

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