The Mediator pattern is a behavioral design pattern that defines an object that encapsulates how a set of objects interact. This pattern promotes communication between objects in a controlled and structured manner, reducing the coupling between them by making them communicate through a central mediator.

Characteristics of the Mediator Pattern

1. Decoupling: Reduces direct coupling between objects by making them communicate through a mediator.
2. Centralized Management: Manages interactions between multiple objects in a centralized manner.
3. Simplicity: Simplifies complex interactions by making them pass through a single control point.

Benefits of the Mediator Pattern

• Maintenance: Facilitates system maintenance and modification by centralizing communication logic.
• Extensibility: Allows adding new functionalities and objects without significantly affecting existing code.
• Reusability: Facilitates the reuse of objects regardless of the system they are in, as interaction rules are centralized.

Implementing the Mediator Pattern in JavaScript

Below are examples of how to implement the Mediator pattern using modern ES6 syntax.

Example 1: Simple Mediator

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In this example, Mediador manages the communication between multiple colleagues (Colega). When a colleague sends a message, the mediator ensures all other colleagues receive it.

Example 2: Mediator in a Chat System

Let's simplify a chat system using the Mediator pattern.

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In this example, Chatroom acts as an intermediary between chat participants. Participants can send and receive messages through the chatroom without communicating directly with each other.

Use Cases for the Mediator Pattern

The Mediator pattern is useful in situations where:

1. Complex Interactions: There are complex interactions between multiple objects.
2. Decoupling: You want to reduce direct coupling between objects.
3. Centralized Communication: A central point is needed to manage communication between objects.

Considerations and Best Practices

• Avoid Overload: Although the Mediator pattern centralizes communication, it can become a bottleneck if it handles too many responsibilities.
• Clarity in Interactions: Document interactions managed by the mediator well to facilitate maintenance and understanding of the system.
• Clear Responsibilities: Ensure the mediator handles only communication and not business logic to maintain a separation of responsibilities.

In the next chapter, we will explore the Decorator Pattern and how it can be used to dynamically add responsibilities to objects.