12-Lets_build_our_Store.md

Chapter 12 - Lets build our Store

1. useContext vs Redux.

Both useContext and Redux are used to solve props drilling, a problem faced while passing props between components.

Context API	Redux
Context provides a way to share values between components (throughout the application) without having to explicitly pass a prop through every level of the tree.	Redux is a central store for storing the data of the applications.
Context API is built-in React tool and does not have to be downloaded separately	Redux is an third-party open source library not part of React which provides a central store, and actions to modify the store.
Requires minimal Setup	Requires extensive setup to integrate it with a React Application
Specifically designed for static data, that is not often refreshed or updated	Usefule for both static and dynamic data
Difficult to debug	Easy to debug using Redux dev tool
Useful for small projects	Useful for larger projects

2. Advantage of using Redux Toolkit over Redux.

1. Abstraction and Convenience: Redux Toolkit provides a set of abstractions and conveniences on top of regular Redux, which make it easier to work with and manage the state of your application. This includes features such as the createSlice function for creating slices of state and its associated actions and reducer, and the createStore function for creating a Redux store with pre-configured middleware and enhancers.

2. Immutable updates: Regular Redux requires you to create a new state object every time you make an update, which can become repetitive and error-prone. Redux Toolkit provides a way to update the state immutably, using its built-in createSlice function.

3. Simplified Reducers: In regular Redux, you write your own reducers, which can become complex and difficult to manage as your application grows. With Redux Toolkit, you can use the createSlice function to generate reducers for you, based on the state updates you define.

4. Improved Performance: Redux Toolkit uses advanced performance optimizations, such as memoization, lazy evaluation, and selective updates, to make your application faster and more efficient.

5. Better Debugging: Redux Toolkit provides better debugging tools, such as the ability to log and replay actions, inspect the current state of your application, and easily track the changes made to your state over time.

3. Explain Dispatcher.

A dispatcher is a function that dispatches actions to the store. In Redux, actions are used to describe changes to the state, and dispatching an action is the way to trigger those changes.

• How to create & use dispatcher function ?

const dispatch = useDispatch();

This hook returns a reference to the dispatch function from the Redux store. You may use it to dispatch actions as needed.

dispatch(actionCreator(data)); // returns an action payload object

When you dispatch an action creator, it returns an action object that the reducer function uses to update the state. The dispatcher function is used to dispatch the action creator and which in turns calls the reducer function to trigger the update.

4. Explain Reducer.

A reducer is a pure function in Redux that takes the current state of your application and an action, and returns a new state based on that action.

Example :

addItem: (state, action) => {
   const item = state.items[action.payload.id];
   const quantity = item && item.hasOwnProperty('quantity')
     ? state.items[action.payload.id]?.quantity + 1 : 1;
   state.items[action.payload.id] = { ...action.payload, quantity };
   state.totalItemsCount = state.totalItemsCount + 1;
},

Here based on the action object, the state is updated inside teh reducer function.

5. Explain slice.

In Redux Toolkit, a slice is a piece of the state that is managed by a single set of actions and reducer.

6. Explain selector.

• A selector is a pure function that takes the current state of your application and returns a derived value based on that state.

• useSelector is a hook from the react-redux library that allows you to subscribe to the state of your Redux store from a React component.

• The useSelector hook takes a selector function as its argument, which is used to extract data from the state tree.

• The component will re-render whenever the state of your Redux store changes and the derived value returned by the selector function changes.

const totalItemsCount = useSelector((store) => store.cart.totalItemsCount);

store => store.cart.totalItemsCount is the selector function which returns the totalItemsCount from the state.

Now, useSelector() is used to subscribe to this totalItemsCount from the state.

7. Explain createSlice and the configuration it takes.

The createSlice function is used to create a store slice, a piece of the store.

The createSlice function takes an object as an argument, which contains the following properties:

• name: A string that represents the name of the slice.
• initialState: An object that represents the initial state of the slice. In our cartSlice example, the initial state is an object with two properties: items (an empty object) and totalItemsCount (which is 0).
• reducers: An object that contains the Redux reducers for the slice. Reducers are functions that take the current state and an action, and return a new state based on the action type and payload. In our example, there are three reducers: addItem, removeItem, and clearCart.

After creating the slice, the code exports the actions that can be dispatched on the store. In this example, there are three actions: addItem, removeItem, and clearCart.

Finally, the code exports the reducer for the slice using the reducer property of the slice. The reducer is responsible for managing the state of the slice and updating it in response to dispatched actions.