What Is React and Why Should You Learn It?

Understanding React

React is a JavaScript library for building user interfaces, created by Facebook (now Meta) in 2013. It is not a framework — it focuses exclusively on the view layer, giving you the freedom to choose your own tools for routing, state management, and backend communication.

Why React Dominates Frontend Development

React holds over 40% market share among JavaScript libraries and frameworks. Here is why:

Component-Based Architecture — React applications are built from small, reusable pieces called components. Each component manages its own markup, logic, and often its styling. This makes complex UIs manageable because you build them from simple, composable building blocks.

Declarative Rendering — Instead of manually manipulating the DOM (like jQuery), you describe what the UI should look like for any given state, and React figures out how to update the screen efficiently.

// Imperative (jQuery approach)
$('#counter').text(count);
if (count > 10) {
  $('#warning').show();
}

// Declarative (React approach)
function Counter({ count }) {
  return (
    <div>
      <p>{count}</p>
      {count > 10 && <p className="warning">High count!</p>}
    </div>
  );
}

Virtual DOM — React maintains a lightweight copy of the real DOM in memory. When state changes, React calculates the minimal set of DOM operations needed and batches them for maximum performance. You never worry about manual DOM updates.

Massive Ecosystem — React has the largest ecosystem of any frontend library: Next.js for full-stack applications, React Native for mobile apps, Redux for state management, thousands of UI component libraries, and more job listings than any other frontend technology.

React vs Angular vs Vue

React's flexibility is both its strength and its challenge. You make architectural decisions that Angular makes for you. This course guides you through those decisions with battle-tested patterns used by top engineering teams.

What You Need to Know Before Starting

You need basic HTML, CSS, and JavaScript knowledge. If you can write a function, use an array, and style a div, you are ready. Chapter 2 refreshes every JavaScript concept React depends on, so even if your JS is rusty, you will be up to speed quickly.