React: Thinking in Components

React is a JavaScript library for building user interfaces. Its key idea is ‘components’ — small, reusable pieces of UI that each manage their own structure, styling, and behavior. Instead of manipulating the DOM manually, you describe how the UI should look for a given state, and React updates the DOM for you when the state changes. Hooks like useState and useEffect allow you to manage local state and side effects in a clean way. When should you use React? For any project where the UI is dynamic: dashboards, SaaS apps, admin tools, multi-step forms, or anything with complex user interaction. For simple static landing pages, plain HTML/CSS or Next.js server-rendered pages might be enough. A mental example: You have a TodoList component with a list of tasks in state. When the user submits a form, you add a new task to the array. React re-renders the list, and the UI updates automatically. No manual DOM query or innerHTML needed. React becomes even more powerful when paired with Next.js, TypeScript, and a design system. You get routing, data fetching, and type safety on top of your components.