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Summary - Context

Set up a theme (dark/light) context and connect two buttons.

Summary - Context

In this group you learned what context is, why it's an alternative to prop drilling, how to create a context object with createContext, provide a value with Provider, and read it with useContext.

The recipe: put global data in context, wrap with a Provider at the top, read with useContext at the bottom. This eliminates prop drilling and keeps code clean.

In the next step you'll combine the provider and the consumer in one file.

Practice Create and read ThemeBadge

Complete the skeleton. Create ThemeContext with default "light". Then write a ThemeBadge component that reads the theme with useContext(ThemeContext) and returns <p>{ '{ theme }' }</p>. Export it.

Starter code

App.jsx
import { createContext, useContext } from "react";

// Define ThemeContext and ThemeBadge here

Sample solution

App.jsx
import { createContext, useContext } from "react";

const ThemeContext = createContext("light");

function ThemeBadge() {
  const theme = useContext(ThemeContext);
  return <p>{theme}</p>;
}

export default ThemeBadge;

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Where does useContext read from?

  • From state
  • The nearest Provider Correct answer
  • From props
  • The farthest Provider

Explanation: useContext reads from the nearest Provider.

2 Match the context steps

Term Meaning
createContext Make object
Provider Give value
useContext Read
value Carry data

All lessons in Beginner

1 React intro

  1. What is React?
  2. Setup and Vite
  3. Your first component
  4. Summary - React intro

2 JSX basics

  1. What is JSX?
  2. Expressions and curly braces
  3. Attributes and className
  4. Summary - JSX basics

3 Components

  1. Component logic
  2. Component tree
  3. Naming rules
  4. Summary - Components

4 Profile card

  1. Project: Profile card
  2. Avatar component
  3. Info list
  4. Assemble the card

5 Props

  1. What are props?
  2. Reading props
  3. Children prop
  4. Default props
  5. Summary - Props

6 Conditional rendering

  1. What is conditional rendering?
  2. Ternary operator
  3. Logical AND (&&)
  4. Early return
  5. Summary - Conditional rendering

7 List rendering

  1. What is list rendering?
  2. The key attribute
  3. Array to components
  4. Filtering and sorting
  5. Summary - List rendering

8 Shopping list

  1. Project: Shopping list
  2. Item component
  3. List body
  4. Empty state

9 Events

  1. Events
  2. The event object
  3. Form events
  4. Summary - Events

10 useState

  1. What is state?
  2. The useState call
  3. Updating state
  4. Multiple state values
  5. Summary - useState

11 Counter app

  1. Project: Counter app
  2. Number and buttons
  3. Decrement and reset
  4. Boundary control

12 Forms

  1. Controlled input
  2. Form submission
  3. Multiple fields
  4. Summary - Forms

13 Styling

  1. Styling with CSS
  2. CSS Modules
  3. Inline styles
  4. Summary - Styling

14 styled-components

  1. What is styled-components?
  2. Styling with props
  3. Using themes
  4. Summary - styled-components

15 useReducer

  1. What is useReducer?
  2. Action and state
  3. useState vs useReducer
  4. Summary - useReducer

16 useEffect

  1. What is useEffect?
  2. Dependency array
  3. Cleanup function
  4. Summary - useEffect

17 Context

  1. What is context?
  2. createContext
  3. Provider and useContext
  4. Summary - Context

18 useRef

  1. What is useRef?
  2. DOM access
  3. Timer example
  4. Summary - useRef

19 Todo app

  1. Project: Todo app
  2. Todo entry form
  3. Todo list
  4. Filter and summary

20 Beginner final

  1. Challenge: Weather card
  2. Challenge: Cart summary
  3. Challenge: Counter and reset
  4. Challenge: Dropdown menu