Aprenda Combining Patterns | Applying Patterns in Real Projects

When you build real-world JavaScript applications, you rarely use design patterns in isolation. Instead, you often combine multiple patterns to solve different parts of a problem, creating solutions that are both flexible and maintainable. By composing patterns, you can address a wider range of challenges and build more robust code. The key is to understand how patterns interact and complement each other, allowing you to leverage their strengths while minimizing complexity.


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// Module pattern to encapsulate chat logic
const ChatModule = (function() {
  // Private list of observers (subscribers)
  const observers = [];

  // Add observer (subscriber)
  function subscribe(fn) {
    observers.push(fn);
  }

  // Notify all observers of a new message
  function notify(message) {
    observers.forEach(fn => fn(message));
  }

  // Public API
  return {
    sendMessage: function(message) {
      console.log("User sent:", message);
      notify(message);
    },
    onMessage: function(fn) {
      subscribe(fn);
    }
  };
})();

// Observer pattern: components subscribe to chat messages
// User 1 subscribes to receive messages
ChatModule.onMessage(function(msg) {
  console.log("User 1 received:", msg);
});

// User 2 subscribes to receive messages
ChatModule.onMessage(function(msg) {
  console.log("User 2 received:", msg);
});

// Sending a message
ChatModule.sendMessage("Hello, everyone!");

By combining the Module and Observer patterns in this chat application, you keep your core logic encapsulated and private while allowing different parts of your code to react to events. This approach brings several benefits. It improves code organization, makes it easier to add or remove features, and supports code reuse by separating concerns. However, combining multiple patterns can also have pitfalls. If you overuse patterns or mix too many together without a clear purpose, your code can become more complicated than necessary. This can lead to overengineering, making your project harder to understand and maintain. Always evaluate whether combining patterns truly adds value to your specific application.

1. Combining design patterns in a project can:

2. What is a potential pitfall of combining multiple patterns?

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Seção 5. Capítulo 2

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// Module pattern to encapsulate chat logic
const ChatModule = (function() {
  // Private list of observers (subscribers)
  const observers = [];

  // Add observer (subscriber)
  function subscribe(fn) {
    observers.push(fn);
  }

  // Notify all observers of a new message
  function notify(message) {
    observers.forEach(fn => fn(message));
  }

  // Public API
  return {
    sendMessage: function(message) {
      console.log("User sent:", message);
      notify(message);
    },
    onMessage: function(fn) {
      subscribe(fn);
    }
  };
})();

// Observer pattern: components subscribe to chat messages
// User 1 subscribes to receive messages
ChatModule.onMessage(function(msg) {
  console.log("User 1 received:", msg);
});

// User 2 subscribes to receive messages
ChatModule.onMessage(function(msg) {
  console.log("User 2 received:", msg);
});

// Sending a message
ChatModule.sendMessage("Hello, everyone!");

1. Combining design patterns in a project can:

2. What is a potential pitfall of combining multiple patterns?

Tudo estava claro?

Obrigado pelo seu feedback!

Seção 5. Capítulo 2