README.md

Mediator Pattern

The Mediator pattern is used to reduce the complexity of communication between multiple objects or classes. Instead of having objects communicate directly with each other, they communicate through a mediator object.

Example

class Mediator {
  constructor() {
    this.colleagues = [];
  }

  register(colleague) {
    this.colleagues.push(colleague);
    colleague.setMediator(this);
  }

  send(message, sender) {
    this.colleagues.forEach((colleague) => {
      if (colleague !== sender) {
        colleague.receive(message);
      }
    });
  }
}

class Colleague {
  constructor(name) {
    this.name = name;
    this.mediator = null;
  }

  setMediator(mediator) {
    this.mediator = mediator;
  }

  send(message) {
    console.log(`${this.name} sends: ${message}`);
    this.mediator.send(message, this);
  }

  receive(message) {
    console.log(`${this.name} receives: ${message}`);
  }
}

Explaining the code

1. Mediator Class:

   • Constructor: Initializes an empty array colleagues to keep track of registered colleagues.
   • register(colleague): Adds a colleague to the colleagues array and sets the mediator for that colleague.
   • send(message, sender): Sends a message to all colleagues except the sender. It iterates over the colleagues array and calls the receive method on each colleague that is not the sender.

2. Colleague Class:

   • Constructor(name): Initializes the colleague with a name and sets the mediator to null.
   • setMediator(mediator): Sets the mediator for the colleague.
   • send(message): Sends a message through the mediator. It logs the message being sent and calls the send method on the mediator.
   • receive(message): Logs the message received by the colleague.

Usage

const mediator = new Mediator();

const colleague1 = new Colleague("Colleague1");
const colleague2 = new Colleague("Colleague2");
const colleague3 = new Colleague("Colleague3");

mediator.register(colleague1);
mediator.register(colleague2);
mediator.register(colleague3);

colleague1.send("Hello, World!");
colleague2.send("Hi there!");
colleague3.send("Good day!");

• An instance of the Mediator class is created.
• Three instances of the Colleague class are created with names "Colleague1", "Colleague2", and "Colleague3".
• Each colleague is registered with the mediator using the register method.
• Each colleague sends a message using the send method, which is then relayed to the other colleagues by the mediator.

Summary

The Mediator design pattern helps manage communication between multiple objects by centralizing the communication logic in a mediator object. This reduces the dependencies between the objects, making the system easier to maintain and extend. In this example, the Mediator class handles the communication between instances of the Colleague class, ensuring that messages are sent to all colleagues except the sender.