Component organization in React - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a functional React component named Greeting.

React

function Greeting() {
  return <h1>[1];</h1>;
}

Drag options to blanks, or click blank then click option'

AHello, world!

B"Hello, world!"

C<Hello, world!>

D{Hello, world!}

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving text unquoted inside JSX

Using angle brackets around text

The component must return JSX with a string inside quotes to render text correctly.

2fill in blank

medium

Complete the code to import React's useState hook.

React

import React, [1] from 'react';

Drag options to blanks, or click blank then click option'

AuseEffect

BComponent

CuseState

DuseContext

Attempts:

3 left

💡 Hint

Common Mistakes

Importing useEffect instead of useState

Trying to import Component in functional components

useState is the hook used to add state to functional components.

3fill in blank

hard

Fix the error in the component by completing the return statement correctly.

React

function Welcome() {
  return [1]
}

Drag options to blanks, or click blank then click option'

A<div>Welcome!</div>;

Bdiv>Welcome!</div>;

C"Welcome!";

D<Welcome!>;

Attempts:

3 left

💡 Hint

Common Mistakes

Missing opening angle bracket

Returning plain string without JSX tags

The return must be a valid JSX element wrapped in angle brackets and properly closed.

4fill in blank

hard

Fill both blanks to create a component that uses useState to toggle text.

React

import React, { [1] } from 'react';

function Toggle() {
  const [isOn, setIsOn] = [2](false);
  return (
    <button onClick={() => setIsOn(!isOn)}>
      {isOn ? 'ON' : 'OFF'}
    </button>
  );
}

Drag options to blanks, or click blank then click option'

AuseState

BuseEffect

CuseReducer

DuseContext

Attempts:

3 left

💡 Hint

Common Mistakes

Importing useEffect but calling useState

Using useReducer instead of useState

useState is imported and called to create state and its setter function.

5fill in blank

hard

Fill all three blanks to create a component that fetches data on mount using useEffect.

React

import React, { [1], [2] } from 'react';

function DataFetcher() {
  const [data, setData] = [3](null);

  [1](() => {
    fetch('https://api.example.com/data')
      .then(response => response.json())
      .then(json => setData(json));
  }, []);

  return <pre>{JSON.stringify(data, null, 2)}</pre>;
}

Drag options to blanks, or click blank then click option'

AuseEffect

BuseState

CuseContext

DuseReducer

Attempts:

3 left

💡 Hint

Common Mistakes

Using useContext instead of useState for data

Not importing useEffect

useEffect is imported and used to run code on mount; useState is imported and used to hold data state.

Practice

1. What is the main benefit of organizing React components by their role or feature?

easy

A. It makes the app run faster

B. It automatically fixes bugs in the code

C. It reduces the size of the final app bundle

D. It keeps the code clean and easier to maintain

Solution

1. Step 1: Understand component organization purpose

   Organizing components by role or feature helps keep the codebase structured and clean.

2. Step 2: Identify the main benefit

   This organization makes the code easier to read, maintain, and update over time.

3. Final Answer:

   It keeps the code clean and easier to maintain -> Option D

4. Quick Check:

   Clean code = B [OK]

Hint: Think about code clarity and maintenance benefits [OK]

Common Mistakes:

• Confusing organization with app speed
• Assuming organization reduces bundle size
• Believing organization fixes bugs automatically

2. Which of the following is the correct way to define a simple functional React component named Button?

easy

A. function Button() { return Click me; }

B. class Button extends React.Component { render() { return Click me; } }

C. const Button = () => { Click me }

D. function Button() { Click me }

Solution

1. Step 1: Check functional component syntax

   A functional component returns JSX inside the function body using return statement.

2. Step 2: Identify correct syntax

   function Button() { return Click me; } correctly defines a function returning JSX. const Button = () => { Click me } misses return. class Button extends React.Component { render() { return Click me; } } is a class component, not functional.

3. Final Answer:

   function Button() { return <button>Click me</button>; } -> Option A

4. Quick Check:

   Functional component needs return [OK]

Hint: Functional components must return JSX explicitly [OK]

Common Mistakes:

• Omitting return statement in arrow functions
• Confusing class and functional component syntax
• Not returning JSX from the function

3. Given the code below, what will be rendered on the screen?

function Greeting({ name }) {
  return <h1>Hello, {name}!</h1>;
}

function App() {
  return <Greeting name="Alice" />;
}

medium

A. Error: name is undefined

B. Hello, name!

C. Hello, Alice!

D.

Solution

1. Step 1: Understand props usage in Greeting

   The Greeting component receives a prop called name and uses it inside JSX to display a greeting.

2. Step 2: Check how App uses Greeting

   App passes the string "Alice" as the name prop, so Greeting renders <h1>Hello, Alice!</h1>.

3. Final Answer:

   <h1>Hello, Alice!</h1> -> Option C

4. Quick Check:

   Props passed correctly = C [OK]

Hint: Props replace placeholders with actual values [OK]

Common Mistakes:

• Thinking props are not passed automatically
• Expecting literal 'name' string instead of value
• Confusing JSX tags with strings

4. Identify the error in this React component organization:

function Header() {
  return <header>Welcome</header>;
}

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

medium

A. Footer component is used but not defined or imported

B. Header component should be a class component

C. App component must return a single element without div

D. Header component should not use semantic tags

Solution

1. Step 1: Check component usage in App

   App uses <Header /> and <Footer /> components inside a div.

2. Step 2: Verify component definitions

   Header is defined, but Footer is neither defined nor imported, causing an error.

3. Final Answer:

   Footer component is used but not defined or imported -> Option A

4. Quick Check:

   Undefined component usage = A [OK]

Hint: All used components must be defined or imported [OK]

Common Mistakes:

• Assuming class components are required
• Thinking multiple elements need no wrapper
• Believing semantic tags cause errors

5. You want to organize a React app with a main Dashboard component that uses smaller components like Sidebar, Content, and Footer. Which approach best follows good component organization?

hard

A. Put all JSX for Sidebar, Content, and Footer inside Dashboard's single file

B. Create separate files for Sidebar, Content, and Footer components and import them into Dashboard

C. Write Sidebar, Content, and Footer as functions inside Dashboard component function

D. Combine Sidebar and Footer into one component and Content separately, all in Dashboard file

Solution

1. Step 1: Understand component reusability and clarity

   Separating components into their own files makes code easier to read, reuse, and maintain.

2. Step 2: Evaluate options for organization

   Create separate files for Sidebar, Content, and Footer components and import them into Dashboard creates separate files and imports them, which is best practice. Other options mix concerns or reduce clarity.

3. Final Answer:

   Create separate files for Sidebar, Content, and Footer components and import them into Dashboard -> Option B

4. Quick Check:

   Separate files for components = A [OK]

Hint: Separate components into files for clarity and reuse [OK]

Common Mistakes:

• Putting all code in one file making it messy
• Defining components inside other components unnecessarily
• Combining unrelated components reducing modularity