Exporting and importing components in React - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this React component import?

Given two files, Header.js and App.js, where Header.js exports a component as export default function Header() { return <h1>Welcome</h1>; } and App.js imports it as import Header from './Header'; and renders <Header />, what will be displayed on the page?

React

/* Header.js */
export default function Header() {
  return <h1>Welcome</h1>;
}

/* App.js */
import React from 'react';
import Header from './Header';

export default function App() {
  return (
    <div>
      <Header />
    </div>
  );
}

A The page shows the text 'Header' as plain text.

B The page shows nothing because the import is incorrect.

C The page shows a heading with the text 'Welcome'.

D The page shows an error because Header is not a named export.

💡 Hint

Check how the component is exported and imported using default export.

When a component is exported as default, it can be imported with any name without curly braces. Rendering

will display the returned JSX, which is an

with 'Welcome'.

📝 Syntax

intermediate

Which import statement correctly imports a named export?

If a React component is exported as export function Footer() { return <footer>Bye</footer>; }, which import statement correctly imports it in another file?

React

export function Footer() {
  return <footer>Bye</footer>;
}

A import { Footer } from './Footer';

B import Footer from './Footer';

C import * as Footer from './Footer';

D import Footer() from './Footer';

💡 Hint

Named exports require curly braces in import.

Named exports must be imported using curly braces with the exact exported name. Option A uses correct syntax.

🔧 Debug

advanced

Why does this import cause an error?

Given export default function Nav() { return <nav>Menu</nav>; } in Nav.js, why does import { Nav } from './Nav'; cause an error?

React

/* Nav.js */
export default function Nav() {
  return <nav>Menu</nav>;
}

/* Another file */
import { Nav } from './Nav';

export default function App() {
  return <Nav />;
}

A Because Nav component is missing a return statement.

B Because Nav is a default export but imported as a named export.

C Because the import path './Nav' is incorrect.

D Because React components cannot be default exported.

💡 Hint

Check the difference between default and named exports and imports.

Default exports must be imported without curly braces. Using curly braces tries to import a named export which does not exist, causing an error.

❓ state_output

advanced

What is the output when importing a component with a typo?

If a component is exported as export default function Sidebar() { return <aside>Links</aside>; } and imported as import SideBar from './Sidebar'; (note the uppercase B), what happens when rendering <SideBar />?

React

/* Sidebar.js */
export default function Sidebar() {
  return <aside>Links</aside>;
}

/* App.js */
import SideBar from './Sidebar';

export default function App() {
  return <SideBar />;
}

A The code throws a runtime error because SideBar is undefined.

B The component renders nothing because the import name is case-sensitive but matches the export.

C The component renders nothing because the import name does not match the export name exactly.

D The component renders correctly showing 'Links'.

💡 Hint

Default exports can be imported with any name regardless of case.

Default exports can be imported with any variable name, so the case difference in the import name does not affect rendering.

🧠 Conceptual

expert

Which statement about exporting and importing React components is true?

Consider these statements about exporting and importing React components. Which one is true?

A Named exports require curly braces when importing, and the imported name must match exactly.

B A component exported as default must be imported with the same name as the export function.

C You can import a default export using curly braces if you rename it.

D You cannot have both named and default exports in the same file.

💡 Hint

Think about how named exports and imports work in JavaScript modules.

Named exports must be imported with curly braces and the exact exported name. Default exports can be imported with any name without braces.