React is a declarative, efficient, and flexible JavaScript library for building user interfaces (UI). It lets you compose complex UIs from small and isolated pieces of code called “components”.
Key Concepts
- Components: The building blocks of React. A component is a self-contained module that renders some output (HTML).
- Virtual DOM: React creates an in-memory data structure cache, computes the resulting differences, and then updates the browser’s displayed DOM efficiently. This makes it very fast.
- JSX: A syntax extension for JavaScript that looks like HTML. It makes writing the UI structure easier and more intuitive within JavaScript code.
Hooks
Introduced in React 16.8, Hooks allow function components to have access to state and other React features. Common hooks include useState (for managing memory) and useEffect (for side effects like data fetching).
Frequently Asked Questions
1. Is React a framework or a library? React is technically a library because it focuses only on the View layer. Frameworks like Angular offer a complete solution (routing, HTTP, etc.), while React often requires additional libraries for those tasks.
2. Why is React so popular? Its component-based architecture, the support of Facebook, a massive ecosystem, and the ability to build mobile apps (React Native) make it the industry standard.
3. What is the difference between Props and State? Props (properties) are arguments passed into components (like function parameters). State is data managed within the component (like local variables).
4. Is React good for SEO? Traditionally, Single Page Applications (SPAs) built with React had SEO issues. However, using frameworks like Next.js or Astro allows for Server-Side Rendering (SSR), making React excellent for SEO.
5. Is React hard to learn? It has a steep learning curve initially if you don’t know JavaScript well. However, once you grasp the concept of components and props, it becomes very logical.