**Course Title:** Mastering React.js: Building Modern User Interfaces **Section Title:** State Management with Context API and Redux **Topic:** Introduction to Redux architecture: actions, reducers, and store **Introduction** In the previous topics, we covered the basics of React state management, including React Context API and Redux. In this topic, we'll dive deeper into the Redux architecture, focusing on actions, reducers, and the store. By the end of this topic, you'll understand the fundamental concepts of Redux and be able to build a simple Redux application. **What is Redux?** Redux is a predictable, scalable, and maintainable state management solution for React applications. It's a single-source truth for state, ensuring that all components have access to the same state. **Actions** Actions are payloads that trigger state changes in your application. They are objects that describe the action to be performed, and they are used to send data to the reducer. Example: ```javascript // actions.js export const ADD_ITEM = 'ADD_ITEM'; export const REMOVE_ITEM = 'REMOVE_ITEM'; export function addItem(item) { return { type: ADD_ITEM, item }; } export function removeItem(item) { return { type: REMOVE_ITEM, item }; } ``` In the above example, we define two actions: `ADD_ITEM` and `REMOVE_ITEM`. We also define two action creators: `addItem` and `removeItem`, which return objects with the corresponding action types and payloads. **Reducers** Reducers are pure functions that take the current state and an action, and return a new state. They are responsible for updating the state based on the actions dispatched. Example: ```javascript // reducers.js const initialState = []; const reducer = (state = initialState, action) => { switch (action.type) { case ADD_ITEM: return [...state, action.item]; case REMOVE_ITEM: return state.filter((item) => item!== action.item); default: return state; } }; export default reducer; ``` In the above example, we define a reducer function that takes the current state and an action as arguments. Based on the action type, it returns a new state by either adding or removing an item from the current state. **Store** The store is the central repository of state in your application. It's the glue that connects the actions and reducers together. Example: ```javascript // store.js import { createStore } from 'redux'; import reducer from './reducers'; const store = createStore(reducer); export default store; ``` In the above example, we create a store using the `createStore` function from the Redux library. We pass the reducer function to it, and it returns a store object that manages the state. **Connecting Redux to React** To connect Redux to your React application, you need to create a higher-order component (HOC) that wraps your React components and connects them to the Redux store. Example: ```javascript // connect.js import { connect } from 'react-redux'; import React from 'react'; const Counter = (props) => { return <div>{props.count}</div>; }; const mapStateToProps = (state) => { return { count: state.counter, }; }; const mapDispatchToProps = (dispatch) => { return { onIncrement: () => dispatch({ type: 'INCREMENT' }), }; }; export default connect(mapStateToProps, mapDispatchToProps)(Counter); ``` In the above example, we define a `Counter` component that displays the current count. We use the `connect` function from the Redux library to connect the component to the Redux store. We pass two functions as arguments: `mapStateToProps` and `mapDispatchToProps`. `mapStateToProps` maps the state to the component props, while `mapDispatchToProps` maps the dispatch function to the component props. **Conclusion** In this topic, we covered the fundamental concepts of Redux architecture, including actions, reducers, and the store. We also learned how to connect Redux to React using a higher-order component. By applying these concepts, you can build a simple Redux application that manages state and dispatches actions. **Leave a comment or ask for help if you have any questions or need further clarification on any of the topics covered in this topic.** In the next topic, we'll explore how to integrate Redux with React, including creating a Redux reducer and dispatching actions. Please wait while I compile the next topic... **Topic:** Integrating Redux with React **Next topic:**