Reusable component APIs

What this means

A component API is the set of props a component accepts. Good APIs are small, clear, and hard to misuse.

In beginner terms, this topic answers one practical question: "What should I write, and why does React care about it?" Do not try to memorize the syntax first. First understand the idea, then connect the syntax to that idea.

Why it matters

Reusable components are not just about code reuse. They create consistent behavior and design across the app.

When you build real React screens, this idea helps you decide where data should live, what the user should see, and what should happen after an interaction. That is why this lesson is part of the main path instead of being an optional detail.

Step by step

1. Notice the UI problem this topic solves. 2. Look at the smallest possible example. 3. Change one value and predict what should appear. 4. Run the example and compare the result with your prediction. 5. Use the practice task before moving on.

Small example

function Button({ children, variant = "primary" }) {
  return <button data-variant={variant}>{children}</button>;
}

Common mistake

Do not add props before there is a real need. Too many props make a component harder to understand.

Practice task

Design a Button component with children and a variant prop.

Remember this

Good components are easy to use correctly.