React

Components are the core building blocks, and JSX is how you write them.

Props pass data between components and make them reusable.

State is a component's memory — what makes the UI change and react.

Events connect user interaction to your app's logic in React.

Showing different parts based on state is the basis of any dynamic UI.

Rendering data as lists is a daily task, and keys let React update them efficiently.

useEffect connects components to the outside world: APIs, timers, subscriptions.

Most apps collect user input — mastering forms in React is essential.

When components share data, you lift state to their closest common parent.

Context solves passing props through many layers (prop drilling).

As state logic grows, useReducer organizes it better than useState.

Custom hooks let you reuse stateful logic across components.

Connecting your UI to real servers is what turns it into an actual app.

Large apps need optimization to avoid wasteful re-renders.

Multi-page apps need routing to move users between views.

Next.js is a React framework giving you routing and server rendering out of the box.