Discover how React Tracked optimizes render performance in web apps. Build a to-do app using two methods, and gain skills to create advanced applications efficiently.

React Tracked is a small library for global state with React Hooks and
React Context. It allows you to develop a small web app with global state
without a bigger library like Redux.

In this course, you will create a to-do app. But before diving into
creating an application, you’ll first learn how React Tracked can solve
common performance issues around render optimization. Once you learn how to
work with this library, you’ll then build a to-do app through two different
methods.

By the end of this course, you will be ready to build more advanced
applications without having to do unnecessary re-rendering. You’ll also
have a nice piece to showcase in your portfolio.

React Tracked: Creating Web Apps with Global State

# Installing React Tracked

In this course, the platform already has React Tracked installed.

If you run the code locally, please [follow the instructions here](https://github.com/dai-shi/react-tracked#install).

# Modify code

Previously, we had the following code for our counter app:

```javascript
const Context = createContext(null);
 
const useGlobalState = () => {
  const value = useContext(Context);
  if (value === null) throw new Error('Please add GlobalStateProvider');
  return value;
};
 
const GlobalStateProvider = ({ children }) => (
  <Context.Provider value={useValue()}>{children}</Context.Provider>
);
```

This creates a context, a hook, and a provider.

In React Tracked, this is done by `createContainer`.

```javascript
import { createContainer } from 'react-tracked';

const {
  useTracked: useGlobalState,
  Provider: GlobalStateProvider,
} = createContainer(useValue);
```

Notice we simply rename a hook and a provider from the default names in a container.

# Check the app

Now, let's try the modified app.

In this lesson, we use React Tracked in the counter app and see how it behaves.

Creating a Counter App only with React Context

Introducing React Tracked to the Counter App

Developing ToDo App with React Tracked and useReducer

Developing ToDo App with React Tracked, useState and Immer

Going Further

Modifying the Counter App with React Tracked

Installing React Tracked #

Modify