Context best practices in React - Mini Project: Build & Apply

Context Best Practices in React

📖 Scenario: You are building a simple React app that shares a theme color across multiple components without passing props manually.

🎯 Goal: Create a React app that uses Context to provide a theme color to nested components following best practices.

📋 What You'll Learn

Create a context with React.createContext

Provide the context value using a Context.Provider

Consume the context value in a child component using useContext hook

Follow best practices for naming and structure

💡 Why This Matters

🌍 Real World

Sharing global data like themes, user info, or settings across many components without passing props manually.

💼 Career

Understanding React Context is essential for building scalable React apps and is a common requirement in frontend developer roles.

1

Create the Theme Context

Create a context called ThemeContext using React.createContext with the default value 'light'.

React

# Create ThemeContext with default value 'light'
# Your code here

Hint

Use React.createContext('light') and assign it to ThemeContext.

2

Add Theme Provider Component

Create a functional component called ThemeProvider that returns ThemeContext.Provider with the value 'dark' and renders its children inside.

React

import React from 'react';

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

// Create ThemeProvider component that provides 'dark' theme
# Your code here

Hint

Wrap {children} inside ThemeContext.Provider with value 'dark'.

3

Consume Theme Context in Child Component

Create a functional component called ThemedButton that uses the useContext hook to get the theme from ThemeContext and renders a button with text showing the current theme.

React

import React from 'react';

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

function ThemeProvider({ children }) {
    return {children};
}

// Create ThemedButton component that uses useContext to get theme
# Your code here

Hint

Use const theme = useContext(ThemeContext) inside ThemedButton and display it inside a button.

4

Use ThemeProvider and ThemedButton in App

Create a functional component called App that uses ThemeProvider to wrap ThemedButton and export App as default.

React

import React, { useContext } from 'react';

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

function ThemeProvider({ children }) {
    return {children};
}

function ThemedButton() {
    const theme = useContext(ThemeContext);
    return {`Current theme is ${theme}`};
}

// Create App component that uses ThemeProvider to wrap ThemedButton
# Your code here

Hint

Wrap ThemedButton inside ThemeProvider in App and export App as default.

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