Context best practices in React - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a React context with a default value.

React

const MyContext = React.[1]('default');

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

AcreateContext

BuseContext

CuseState

DcreateState

Attempts:

3 left

💡 Hint

Common Mistakes

Using useContext instead of createContext

Trying to use useState to create context

Use React.createContext to create a new context with a default value.

2fill in blank

medium

Complete the code to consume a context value inside a functional component.

React

const value = React.[1](MyContext);

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

AuseContext

BuseState

CuseEffect

DcreateContext

Attempts:

3 left

💡 Hint

Common Mistakes

Using createContext instead of useContext

Trying to use useState to get context

Use useContext hook to read the current context value inside a component.

3fill in blank

hard

Fix the error in the code to properly provide a context value.

React

<MyContext.Provider value=[1]>
  <ChildComponent />
</MyContext.Provider>

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

A{{value}}

B{value}

Cvalue

D[value]

Attempts:

3 left

💡 Hint

Common Mistakes

Passing value without curly braces

Using double curly braces which is incorrect syntax

The value prop must be passed as a JavaScript expression inside curly braces.

4fill in blank

hard

Fill both blanks to create a context and export its provider component.

React

const [1] = React.createContext();

export const [2] = [1].Provider;

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

AThemeContext

BUserContext

CThemeProvider

DUserProvider

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing context and provider names

Not exporting the provider correctly

Create a context named ThemeContext and export its Provider as ThemeProvider.

5fill in blank

hard

Fill all three blanks to consume context and display its value in a component.

React

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

function Display() {
  const value = [2](MyContext);
  return <p>The value is: [3]</p>;
}

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

AuseContext

BuseState

Cvalue

DuseEffect

Attempts:

3 left

💡 Hint

Common Mistakes

Importing wrong hooks

Using wrong variable names in JSX

Import and use useContext to get the context value, then display it inside the paragraph.

Practice

1. What is the main purpose of React Context?

easy

A. To handle routing between pages

B. To style components globally

C. To manage component local state only

D. To share data between components without passing props manually

Solution

1. Step 1: Understand React Context role

   React Context allows sharing data across many components without passing props at every level.

2. Step 2: Compare with other options

   Styling, local state, and routing are handled by other React features or libraries, not Context.

3. Final Answer:

   To share data between components without passing props manually -> Option D

4. Quick Check:

   Context shares data without prop drilling [OK]

Hint: Context shares data without passing props repeatedly [OK]

Common Mistakes:

• Confusing Context with styling or routing
• Thinking Context manages only local state
• Assuming Context replaces all state management

2. Which of the following is the correct way to create a Context in React?

easy

A. const MyContext = new Context();

B. const MyContext = createContext();

C. const MyContext = React.createContext();

D. const MyContext = React.useContext();

Solution

1. Step 1: Recall Context creation syntax

   React Context is created using React.createContext() function.

2. Step 2: Check other options

   A uses invalid constructor, B misses React prefix, D calls a hook instead of creating context.

3. Final Answer:

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

4. Quick Check:

   Use React.createContext() to create context [OK]

Hint: Create context with React.createContext() [OK]

Common Mistakes:

• Omitting React prefix
• Using new keyword incorrectly
• Confusing useContext hook with createContext

3. Given this code snippet, what will be logged to the console?

const ThemeContext = React.createContext('light');

function DisplayTheme() {
  const theme = React.useContext(ThemeContext);
  console.log(theme);
  return <div>Current theme: {theme}</div>;
}

function App() {
  return (
    <ThemeContext.Provider value="dark">
      <DisplayTheme />
    </ThemeContext.Provider>
  );
}

medium

A. "dark"

B. "light"

C. undefined

D. Error: useContext called outside Provider

Solution

1. Step 1: Identify Provider value

   The ThemeContext.Provider wraps DisplayTheme with value "dark".

2. Step 2: Understand useContext behavior

   useContext reads the nearest Provider value, so theme is "dark" inside DisplayTheme.

3. Final Answer:

   "dark" -> Option A

4. Quick Check:

   useContext reads Provider value, not default [OK]

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

Common Mistakes:

• Assuming default value is used despite Provider
• Thinking useContext returns undefined without explicit value
• Confusing useContext with useState

4. What is wrong with this React Context usage?

const UserContext = React.createContext();

function Profile() {
  const user = React.useContext(UserContext);
  return <div>User: {user.name}</div>;
}

function App() {
  return <Profile />;
}

medium

A. UserContext.Provider is missing, so user is undefined causing error

B. useContext hook is used incorrectly inside Profile

C. React.createContext() requires a default value

D. Profile component should not access context directly

Solution

1. Step 1: Check for Provider wrapping

   App renders Profile without wrapping it in UserContext.Provider, so context value is undefined.

2. Step 2: Understand consequence in Profile

   Accessing user.name when user is undefined causes runtime error.

3. Final Answer:

   UserContext.Provider is missing, so user is undefined causing error -> Option A

4. Quick Check:

   Missing Provider means context value is undefined [OK]

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

Common Mistakes:

• Thinking createContext must have default value
• Believing useContext usage is incorrect here
• Assuming components can't access context directly

5. You want to update a theme value shared via Context from a nested component. Which is the best practice to enable this?

hard

A. Use useState inside the nested component to update theme locally

B. Pass a setter function in the Context value and call it inside the nested component

C. Create a new Context inside the nested component to override theme

D. Modify the Context object directly without Provider

Solution

1. Step 1: Understand Context update pattern

   To update shared data, pass a setter function (like from useState) in Context value.

2. Step 2: Evaluate other options

   Using local useState won't update shared theme; creating new Context breaks sharing; modifying Context object directly is invalid.

3. Final Answer:

   Pass a setter function in the Context value and call it inside the nested component -> Option B

4. Quick Check:

   Pass setter in Context to update shared state [OK]

Hint: Pass setter function via Context to update shared state [OK]

Common Mistakes:

• Trying to update Context value directly
• Using local state instead of shared state
• Creating multiple Contexts unnecessarily