In frontend development, one of the biggest challenges is offering a fluid and fast user experience. Modern users expect applications that respond immediately, without delays or interruptions. This is where the concept of Optimistic UI.

What is Optimistic UI?

Optimistic UI, or Optimistic User Interface, is a development technique in which the application immediately assumes the success of a user action and updates the interface accordingly, even before receiving confirmation from the server.

Advantages of Optimistic UI

1. - Improve user experience: By reducing the perceived wait time, the application feels faster and more responsive.
2. - Increases interactivity: Users can continue interacting with the application without interruptions.
3. - Reduced friction: Minimizes user frustration by not having to wait for actions to complete.

Optimistic UI Implementation

To illustrate how to implement Optimistic UI, let's consider a common example: a task application where users can add and remove items from a list.

Step 1: Optimistic UI Update

First, we update the UI immediately after the user performs an action, such as adding a new task.

const addTask = async (newTask) => {
  // Actualización optimista de la UI
  setTasks([...tasks, newTask]);

  try {
    // Enviar la nueva tarea al servidor
    await api.addTask(newTask);
  } catch (error) {
    // Revertir la UI en caso de error
    setTasks(tasks);
    console.error('Error al añadir la tarea:', error);
  }
};

Step 2: Error Handling

It is crucial to handle possible server errors and roll back the UI in case something goes wrong.

const addTask = async (newTask) => {
  const previousTasks = [...tasks];

  // Actualización optimista de la UI
  setTasks([...tasks, newTask]);

  try {
    // Enviar la nueva tarea al servidor
    await api.addTask(newTask);
  } catch (error) {
    // Revertir la UI en caso de error
    setTasks(previousTasks);
    console.error('Error al añadir la tarea:', error);
  }
};

Step 3: Synchronization with the server

In some cases, it may be necessary to synchronize the UI state with the server after performing several optimistic actions.

const syncTasksWithServer = async () => {
  try {
    const serverTasks = await api.getTasks();
    setTasks(serverTasks);
  } catch (error) {
    console.error('Error al sincronizar las tareas con el servidor:', error);
  }
};

// Llamada a la función de sincronización en intervalos regulares o en ciertos eventos
useEffect(() => {
  const interval = setInterval(syncTasksWithServer, 60000);
  return () => clearInterval(interval);
}, []);

Use cases for Optimistic UI

Optimistic UI is especially useful in applications where server latency can impact the user experience:

• Messaging applications: Send messages without waiting for confirmation from the server.
• Content management systems: Edit and publish content without delays.
• E-commerce platforms: Add or remove products from the shopping cart instantly.

Conclusion

Optimistic UI is a powerful technique that can transform the user experience in your applications, making them faster and more fluid. Although it requires careful error handling and synchronization, the benefits far outweigh the challenges.