Creating context in React - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new React context.

React

import React from 'react';
const MyContext = React.[1]();

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

AuseContext

BuseState

CcreateContext

DuseEffect

Attempts:

3 left

💡 Hint

Common Mistakes

Using useContext instead of createContext

Trying to use useState or useEffect here

The createContext function is used to create a new React context object.

2fill in blank

medium

Complete the code to provide the context value to child components.

React

function MyProvider({ children }) {
  return (
    <MyContext.Provider value={{ name: 'Alice' }}>
      [1]
    </MyContext.Provider>
  );
}

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

AMyContext.Consumer

B<MyContext.Consumer />

C<div>children</div>

Dchildren

Attempts:

3 left

💡 Hint

Common Mistakes

Wrapping children inside a div unnecessarily

Using MyContext.Consumer here instead of children

The children prop represents the nested components that will receive the context.

3fill in blank

hard

Fix the error in the code to consume the context value inside a component.

React

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

function MyComponent() {
  const context = [1](MyContext);
  return <div>{context.name}</div>;
}

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

AuseContext

BcreateContext

CuseState

DuseEffect

Attempts:

3 left

💡 Hint

Common Mistakes

Importing createContext instead of useContext

Trying to use useState or useEffect here

The useContext hook is used to read the current context value inside a component.

4fill in blank

hard

Fill both blanks to create and export a context with a default value.

React

import React from 'react';

const [1] = React.[2]({ name: 'Guest' });

export default [1];

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

AUserContext

BcreateContext

CuseContext

DMyContext

Attempts:

3 left

💡 Hint

Common Mistakes

Using useContext instead of createContext

Exporting the wrong variable name

You create a context named UserContext using createContext with a default value.

5fill in blank

hard

Fill all three blanks to consume context and display a greeting.

React

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

function Greeting() {
  const user = [2](UserContext);
  return <h1>Hello, [3]!</h1>;
}

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

AuseContext

BuseState

Cuser.name

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Using useState instead of useContext

Displaying the whole user object instead of user.name

Use useContext to get the user object, then display user.name in the greeting.

Practice

1. What is the main purpose of React's createContext() function?

easy

A. To manage local component state

B. To create a new React component

C. To fetch data from an API

D. To create a context object that allows sharing data without passing props manually

Solution

1. Step 1: Understand what createContext() does

   This function creates a context object that can hold data to be shared across components without passing props manually.

2. Step 2: Compare with other options

   Creating components, fetching data, or managing local state are unrelated to createContext().

3. Final Answer:

   To create a context object that allows sharing data without passing props manually -> Option D

4. Quick Check:

   Purpose of createContext() = share data without props [OK]

Hint: Remember: createContext() sets up shared data space [OK]

Common Mistakes:

• Confusing context creation with component creation
• Thinking it fetches data from APIs
• Mixing it up with useState for local state

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

easy

A. const MyContext = useContext();

B. const MyContext = React.createContext();

C. const MyContext = createContext();

D. const MyContext = React.useContext();

Solution

1. Step 1: Identify correct syntax for creating context

   The correct way is to call createContext() from the React object: React.createContext().

2. Step 2: Check other options

   const MyContext = createContext(); misses the React prefix, which causes an error unless imported separately. Options A and D use useContext(), which is for consuming context, not creating it.

3. Final Answer:

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

4. Quick Check:

   Creating context = React.createContext() [OK]

Hint: Use React.createContext() to create context, not useContext() [OK]

Common Mistakes:

• Using useContext() instead of createContext()
• Omitting React prefix without import
• Confusing creation and consumption functions

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

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

function Display() {
  const value = React.useContext(MyContext);
  console.log(value);
  return null;
}

function App() {
  return (
    <MyContext.Provider value="hello">
      <Display />
    </MyContext.Provider>
  );
}

medium

A. "hello"

B. "default"

C. undefined

D. Error: useContext called outside provider

Solution

1. Step 1: Understand context default and provider value

   The context default is "default", but the Display component is inside a provider with value "hello".

2. Step 2: Determine value consumed by useContext

   Since Display is inside the provider, useContext(MyContext) returns "hello".

3. Final Answer:

   "hello" -> Option A

4. Quick Check:

   Provider value overrides default = "hello" [OK]

Hint: Provider value overrides default context value [OK]

Common Mistakes:

• Assuming default value is always used
• Thinking useContext errors without provider
• Confusing string quotes in output

4. Identify the error in the following React context usage:

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

function Button() {
  const theme = React.useContext();
  return <button>Theme is {theme}</button>;
}

medium

A. Provider is missing around Button

B. Context should be created with useContext

C. Missing argument in useContext call

D. Button component must be class-based to use context

Solution

1. Step 1: Check useContext usage

   The useContext hook requires the context object as an argument. Here, it is called without any argument.

2. Step 2: Verify other options

   Context is correctly created with createContext. Provider is optional but not an error here. Functional components can use hooks, so no need for class-based.

3. Final Answer:

   Missing argument in useContext call -> Option C

4. Quick Check:

   useContext requires context argument [OK]

Hint: Always pass context object to useContext() [OK]

Common Mistakes:

• Calling useContext() without argument
• Confusing createContext and useContext
• Thinking Provider is mandatory to avoid errors

5. You want to create a theme context that provides either "light" or "dark" mode to your app. Which approach correctly creates and uses this context with a provider and consumer component?

hard

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

function ThemeProvider({ children }) {
const theme = 'dark';
return (
<ThemeContext.Provider value={theme}>
{children}
</ThemeContext.Provider>
);
}

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

B. const ThemeContext = React.useContext('light');

function ThemeProvider({ children }) {
const theme = 'dark';
return (
<ThemeContext.Provider value={theme}>
{children}
</ThemeContext.Provider>
);
}

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

C. const ThemeContext = React.createContext();

function ThemeProvider({ children }) {
const theme = 'dark';
return (
<ThemeContext.Provider value={theme}>
{children}
</ThemeContext.Provider>
);
}

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

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

function ThemeProvider({ children }) {
const [theme, setTheme] = React.useState('dark');
return (
<ThemeContext.Provider value={theme}>
{children}
</ThemeContext.Provider>
);
}

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

Solution

1. Step 1: Check context creation and default value

   const ThemeContext = React.createContext('light'); function ThemeProvider({ children }) { const theme = 'dark'; return ( <ThemeContext.Provider value={theme}> {children} </ThemeContext.Provider> ); } function DisplayTheme() { const theme = React.useContext(ThemeContext); return <div>Current theme: {theme}</div>; } correctly creates context with default "light" using createContext('light').

2. Step 2: Verify provider and consumer usage

   The provider passes "dark" as value, and consumer uses useContext(ThemeContext) correctly. const ThemeContext = React.createContext('light'); function ThemeProvider({ children }) { const [theme, setTheme] = React.useState('dark'); return ( <ThemeContext.Provider value={theme}> {children} </ThemeContext.Provider> ); } function DisplayTheme() { const theme = React.useContext(ThemeContext); return <div>Current theme: {theme}</div>; } attempts to use state but misses the React. prefix on useState, causing ReferenceError. const ThemeContext = React.useContext('light'); function ThemeProvider({ children }) { const theme = 'dark'; return ( <ThemeContext.Provider value={theme}> {children} </ThemeContext.Provider> ); } function DisplayTheme() { const theme = React.useContext(ThemeContext); return <div>Current theme: {theme}</div>; } incorrectly calls React.useContext('light') instead of createContext(). const ThemeContext = React.createContext(); function ThemeProvider({ children }) { const theme = 'dark'; return ( <ThemeContext.Provider value={theme}> {children} </ThemeContext.Provider> ); } function DisplayTheme() { const theme = React.useContext(); return <div>Current theme: {theme}</div>; } calls useContext() without argument, causing error.

3. Final Answer:

   Correctly creates and uses context with provider and consumer -> Option A

4. Quick Check:

   Correct createContext and useContext with provider = const ThemeContext = React.createContext('light'); function ThemeProvider({ children }) { const theme = 'dark'; return ( <ThemeContext.Provider value={theme}> {children} </ThemeContext.Provider> ); } function DisplayTheme() { const theme = React.useContext(ThemeContext); return <div>Current theme: {theme}</div>; } [OK]

Hint: createContext with default, provider passes value, useContext consumes [OK]

Common Mistakes:

• Using useContext instead of createContext to create context
• Calling useContext without argument
• Not passing provider value or missing provider