What is the observer pattern and how is it implemented in different programming languages?

Can you explain the observer pattern and its use cases?

The observer pattern is a behavioral design pattern where an object, called the subject, maintains a list of its dependents, called observers, and notifies them of state changes. It's commonly used in event handling systems.

How is the observer pattern implemented in Java?

In Java, the observer pattern can be implemented using the Observer interface and the Observable class. Observers register themselves with the observable, and when the observable's state changes, it calls the update method on each registered observer.

What about in Python?

In Python, you can implement the observer pattern using a simple class structure. You can create a subject class that maintains a list of observers and notifies them when its state changes. The observers can be any callable objects.

Can you give an example in JavaScript?

Sure! In JavaScript, you can use a class to represent the subject and an array to hold observers. When the subject's state changes, it can loop through the array and call each observer's update method.