What is a Reducer?

Using redux-toolkit - 

import { configureStore } from '@reduxjs/toolkit';

const store = configureStore({
  reducer: {
    //your reducers
  },
  devTools: process.env.NODE_ENV !== 'production',
});

Redux Thunk is a middleware that allows action creators to return a function instead of an action object. This enables handling asynchronous operations. For example, you can fetch data from an API and dispatch an action once the data is received.

Actions in Redux are plain JavaScript objects that represent an intention to change the state. They must have a 'type' property. For example, an action to add a user might look like this: { type: 'ADD_USER', payload: { id: 1, name: 'John' } }.

The Redux store holds the application's state. It provides methods to access the state, dispatch actions, and register listeners. For example, when an action is dispatched to add a new item, the store updates its state and notifies subscribers.

Redux Toolkit is the official, recommended way to write Redux logic. It simplifies store setup and reduces boilerplate. With features like 'createSlice', it allows for easy state management and action creation, making development faster and more intuitive.

To create a slice in Redux Toolkit, use 'createSlice'. It takes an object with a name, initial state, and reducers. For example: const userSlice = createSlice({ name: 'user', initialState: {}, reducers: { addUser: (state, action) => { state[action.payload.id] = action.payload; } }});.

Redux is a predictable state container for JavaScript apps. It helps manage the state of an application in a centralized way, allowing for easier debugging and testing. For example, in a React app, Redux can store user authentication status, which can be accessed by any component.

createAsyncThunk is a utility in Redux Toolkit for handling asynchronous actions. It simplifies the process of creating thunks. For example: const fetchUser = createAsyncThunk('user/fetch', async (userId) => { const response = await fetch(`/api/users/${userId}`); return response.json(); });.

A reducer is a pure function that takes the current state and an action as arguments, returning a new state. For instance, a user reducer might handle actions like 'ADD_USER' or 'REMOVE_USER' and return the updated user list.

Middleware in Redux provides a way to extend Redux's capabilities, allowing for side effects like API calls. For instance, 'redux-thunk' enables action creators to return functions instead of actions, facilitating asynchronous logic within your app.

Selectors are functions that extract specific pieces of state from the Redux store. They enhance performance and readability. For instance, a selector like 'getUserById' can retrieve a user by their ID, allowing components to access only the necessary data.