Summary  
This chapter covers managing asynchronous data states by evaluating status and error values to conditionally render loading indicators, error messages, or content.  

General domain of usage  
Web user interface development

## The Problem

When working with async data, the UI must react to different states.





## Handling States

You can use the status and error values from the store:

* Show loading indicators;
* Show data when available;
* Show errors when something fails.




```javascript
const { items, status, error } = useSelector((state) => state.posts);

if (status === 'loading') {
  return <p>Loading...</p>;
}

if (status === 'failed') {
  return <p>Error: {error}</p>;
}

return (
  <ul>
    {items.map((post) => (
      <li key={post.id}>{post.title}</li>
    ))}
  </ul>
);
```

Users need feedback.
Without handling these states, the app feels broken or unresponsive.



Learn how to manage complex application state in React using Redux Toolkit. Understand when Redux is actually needed, build state with slices, handle async data, and connect everything into a predictable flow. 

Understand why Redux Toolkit exists and when it becomes useful. Recognize how state complexity grows in real applications and why simple approaches stop scaling.

Install Redux Toolkit and set up the store. Connect Redux to a React application and understand how data flows through the system.

Define state using slices and organize logic clearly. Create reducers, use generated actions, and keep state manageable as the application grows.

Read data from the store using useSelector and update it with useDispatch. Structure state correctly and avoid common mistakes when working with shared data.

Fetch data from APIs using createAsyncThunk. Manage loading and error states and keep the UI in sync with async updates.

Split state into multiple slices and organize files by feature. Combine reducers cleanly and maintain a clear structure as the application grows.

Build a complete application using Redux Toolkit. Implement CRUD features, handle async data, and improve the user experience with loading and error states.

Managing Loading and Error States

The Problem

Handling States