Avoiding prop drilling in React - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a React context.

React

const ThemeContext = React.[1]();

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

AuseEffect

BcreateContext

CuseState

DuseContext

Attempts:

3 left

💡 Hint

Common Mistakes

Using useState instead of createContext

Using useContext to create context (it's for consuming context)

React.createContext() creates a new context object to share data without prop drilling.

2fill in blank

medium

Complete the code to provide context value to child components.

React

<ThemeContext.Provider value=[1]>
  {children}
</ThemeContext.Provider>

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

Atheme

Bcontext

Cstate

Dprops

Attempts:

3 left

💡 Hint

Common Mistakes

Passing props object instead of the specific value

Passing undefined or wrong variable

The value prop of the Provider passes the data (like theme) to children.

3fill in blank

hard

Fix the error in consuming context inside a functional component.

React

const theme = React.[1](ThemeContext);

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

AcreateContext

BuseState

CuseContext

DuseEffect

Attempts:

3 left

💡 Hint

Common Mistakes

Using createContext to consume context

Using useState or useEffect instead of useContext

useContext is the React hook to consume context values inside components.

4fill in blank

hard

Fill both blanks to create a context and provide a default value.

React

const UserContext = React.[1]([2]);

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

AcreateContext

BuseContext

C{}

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using useContext instead of createContext

Passing null when an object is expected

createContext accepts a default value, often an empty object for user data.

5fill in blank

hard

Fill all three blanks to consume context and display a user name.

React

const user = React.[1](UserContext);

// Assume user object has a 'name' property
// Use optional chaining to avoid errors
const displayName = user?.[3] || 'Guest';
return <p>Hello, [2]. Welcome back!</p>;

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

AuseContext

Buser.name

Cname

DcreateContext

EdisplayName

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to access user.name directly without optional chaining

Using createContext instead of useContext to consume

useContext reads the context, displayName holds the safe user name, and name accesses the property.

Practice

1. What is the main problem that prop drilling causes in React applications?

easy

A. Not using hooks properly in functional components

B. Using too many state variables in a single component

C. Rendering components multiple times unnecessarily

D. Passing props through many layers even if intermediate components don't need them

Solution

1. Step 1: Understand what prop drilling means

   Prop drilling happens when props are passed down through many components that don't use them, just to reach a deeply nested component.

2. Step 2: Identify the main issue caused by prop drilling

   This makes the code harder to maintain and understand because many components receive props they don't need.

3. Final Answer:

   Passing props through many layers even if intermediate components don't need them -> Option D

4. Quick Check:

   Prop drilling = Passing props through many layers [OK]

Hint: Prop drilling means unnecessary passing props down layers [OK]

Common Mistakes:

• Confusing prop drilling with state management issues
• Thinking prop drilling is about rendering performance
• Believing prop drilling is caused by hooks misuse

2. Which of the following is the correct way to create a React Context to avoid prop drilling?

easy

A. const MyContext = React.useContext();

B. const MyContext = React.createContext();

C. const MyContext = React.useState();

D. const MyContext = React.useEffect();

Solution

1. Step 1: Recall the React API for creating context

   React provides createContext to create a context object for sharing data.

2. Step 2: Identify the correct syntax

   The correct syntax is const MyContext = React.createContext();. The other options are hooks used for different purposes.

3. Final Answer:

   const MyContext = React.createContext(); -> Option B

4. Quick Check:

   createContext() creates context [OK]

Hint: Use createContext() to make a context object [OK]

Common Mistakes:

• Using useContext() to create context instead of consume it
• Confusing useState() or useEffect() with context creation
• Missing parentheses after createContext

3. Given this code snippet, what will be the output inside Child component?

const MyContext = React.createContext('default');

function Parent() {
  return (
    
      
    
  );
}

function Child() {
  const value = React.useContext(MyContext);
  return <div>{value}</div>;
}

medium

A. <div>hello</div>

B. <div>default</div>

C. <div>undefined</div>

D. Error: useContext must be inside a Provider

Solution

1. Step 1: Understand the context default and provider value

   The context default is 'default', but the Parent component provides the value 'hello' via MyContext.Provider.

2. Step 2: Determine what useContext returns inside Child

   The Child component uses useContext(MyContext), so it receives the nearest provider's value, which is 'hello'.

3. Final Answer:

   <div>hello</div> -> Option A

4. Quick Check:

   useContext returns nearest Provider value [OK]

Hint: useContext gets nearest Provider value, not default [OK]

Common Mistakes:

• Assuming default value is always used
• Thinking useContext returns undefined without explicit value
• Confusing Provider value with component props

4. Identify the error in this code that tries to avoid prop drilling using React Context:

const MyContext = React.createContext();

function Parent() {
  const value = 'data';
  return <Child />;
}

function Child() {
  const value = React.useContext(MyContext);
  return <div>{value}</div>;
}

medium

A. MyContext.Provider is missing around Child component

B. useContext is used incorrectly inside Child

C. createContext must have a default value

D. Parent should pass value as a prop to Child

Solution

1. Step 1: Check if Provider wraps components needing context

   The Parent component returns <Child /> without wrapping it in MyContext.Provider.

2. Step 2: Understand useContext requires Provider to get value

   Without a Provider, useContext(MyContext) returns the default value, which is undefined here, likely not intended.

3. Final Answer:

   MyContext.Provider is missing around Child component -> Option A

4. Quick Check:

   Provider missing = context value undefined [OK]

Hint: Always wrap consumers with Provider to supply context [OK]

Common Mistakes:

• Thinking createContext must have default value
• Believing useContext works without Provider
• Confusing prop passing with context usage

5. You have a deeply nested component tree where ThemeContext provides a theme string. You want to avoid prop drilling and also allow components to update the theme. Which approach correctly combines context and state to achieve this?

hard

A. Use multiple contexts for theme and setTheme separately and pass them as props

B. Pass theme as a prop from top to bottom and use useState only in the deepest component

C. Create ThemeContext with createContext, provide {theme, setTheme} from a state in a top-level component, and consume both in nested components

D. Store theme in a global variable and read it directly in nested components

Solution

1. Step 1: Understand how to share state and updater via context

   To avoid prop drilling and allow updates, the context should provide both the current value and a function to update it.

2. Step 2: Use createContext and provide state and setter from top-level

   Create a context with createContext(), then in a top-level component use useState to hold theme and pass both theme and setTheme in the Provider's value.

3. Step 3: Consume both theme and setTheme in nested components

   Nested components use useContext to get both and can read or update the theme without prop drilling.

4. Final Answer:

   Create ThemeContext with createContext, provide {theme, setTheme} from a state in a top-level component, and consume both in nested components -> Option C

5. Quick Check:

   Context with state and setter avoids prop drilling [OK]

Hint: Provide state and setter in context value to update data [OK]

Common Mistakes:

• Passing only value without setter in context
• Using global variables instead of React state
• Passing props through many layers instead of context