Singleton Pattern

The Module Pattern

The Observer Pattern

The Prototype Pattern

The Factory Pattern

The Adapter Pattern

Learning Resources

Design patterns

https://www.patterns.dev/posts/classic-design-patterns/
https://www.freecodecamp.org/news/javascript-design-patterns-explained/

Task & Assignment

For this exercise, our goal is to create a telephone package. The telephone class should expose 3 different methods.

• AddPhoneNumber - For adding a new phone number
• RemovePhoneNumber - For removing a phone number
• DialPhoneNumber - For dialling a phone number (only phone numbers that have been added can be dialled)

The telephone class should also maintain a list of observers and notify them whenever a phone number is dialled. 

Requirements

1. Create a telephone class. It should expose 3 public methods - AddPhoneNumber, RemovePhoneNumber, and DialPhoneNumber.
2. Update the telephone class, so it uses the observer pattern (have methods to add, remove and notify observers)
3. Create a class for the observer, it should have a method that can be called by the telephone class to notify it. 
4. Have the telephone class notify the observers any time a phone number is dialed. 
5. Add two observers to the telephone class

• 
  
  •  The first one should print the phone number
  •   The second one should print `Now Dialling 2347023232`