fso-helsinki

Part 1 - Introduction to React

• components - independent and reusuable building blocks of a web app
• props - arguements passed into components
• useState - hook that allows you to add a state variable to a component; to manage and store data that changes over time

Part 2 - Communicating with server

• useEffect - hook that allows you to synchronize a component with an external system (ex. fetch data from server); executed after the initial render
• promise - object that represents the eventual completion or failure of an asychronous operation (ex. pending, fulfulled, rejected)

Part 3 - Programming a server with NodeJS and Express

• NodeJS - JavaScript runtime based on Google's Chrome V8 JavaScript engine
• Express - server-side development library used with Node
• REST APIs - allows frontend to interact with backend by sending HTTP requests (ex. GET, POST, PUT, DELETE) and receiving HTTP responses (typically in JSON format)
• middleware - intermediary functions that can process request objects before they reach the backend or response objects before they reach the client; uses next() to pass control to the next route handler/middleware function in the stack (ex. json-parser to parse JSON to JS objects, CORS to enable cross-origin requests, user authentication, logging requests, error handling)
• Mongoose - an ODM for MongoDB that provides a high-level API, allowing interactions with the MongoDB database using JavaScript objects, model application data with schemas, enforce data validation, and simplify database CRUD operations

Part 4 - Testing Express servers, user administration

• supertest - library used for sending HTTP requests to REST API and asserting expected responses
• async/await - simplifies working with promises in asychronous operations (ex. fetching data); async declares function as asychronous, await pauses the execution of the function until the promise resolves, making the code look and behave like synchronous code (allows rest of app to run concurrently)
• bcrypt - package for hasing passwords to securely store them in a database
• jsonwebtoken - library that generates JSON web tokens, enabling token-based authentication (ex. when the user logs in, backend generates a TOKEN that identifies the user)

Part 5 - Testing React apps

• props.children - used to pass components as children to a component (ex. to create togglable component)
• useRef - creates mutable object that persists across re-renders, commonly used to access or stores references to component instances
• useImperativeHandle - customizes the instance value that is exposed when using ref in parent components, often used with forwardRef to make functions available outside of component
• Vitest - used for quick and isolated unit tests (ex. testing React components, mocking API calls to test isolated components)
• Cypress - used for E2E tests within a real browser
• Integration tests - test backend API functionality (ex. making POST request and verifying response and database changes)
• Unit tests - test frontend components in isolation to ensure they render as expected (ex. testing React component to verify it displays correct content when given specific props)
• E2E tests - test entire application flow to ensure frontend and backend work as expected (ex. simulating user logging in, creating post, verifying post appears on interface)

Part 6 - Advanced state management

• Redux - state management library that uses a central store to manage application's state; allows for predictable state changes through actions and reducers; actions are dispatched to modify the state
• useDispatch - provides React components access to the dispatch function of Redux store; used to send actions to update store
• useSelector - allows React components to fetch data from Redux store
• Redux Toolkit - library that simplifies working with Redux (ex. create stores with less boilerplate code, write reducers and action creators using simpler syntax, handle asynchronous actions with thunk)
• configureStore - simplifies setup of Redux store and reducers
• createSlice - combines reducers and action creators into a single API, returning both action creators and the reducer
• action creators - Set up the action and dispatch to reducer
• reducers - functions that processes actions and updates the state
• redux-thunk - middleware that allows action creators to return functions instead of action objects; functions can handle asychronous operations (ex. fetch data from server) and dispatch action (ex. saving data to store); abstracts server communication away from components
• react-query - used to store and manage data retrieved from server
• useReducer - React hook that manages complex state logic by using a reducer functionto handle state updates in response to dispatched actions
• createContext - used to create a context that components can provide or read
• useContext - used to read and subscribe to context from your component
• context - mechanism for sharing state between components without "prop drilling"

Part 7 - React router, custom hooks, styling app with CSS and webpack

• react-router - library for managing navigation in a React app
• useParams - access URL parameter (ex. to fetch specific resource)
• useNavigate - change browser's URL (ex. to render page after login)
• useMatch - access paramaterizied part of path if URL matches (ex. extract ID of resource to fetch actual resource)
• custom hooks - refactor component logic into reusable functions (ex. form field)