React useContext Hook

The useContext hook allows you to share data across components without passing props manually at every level (also known as prop drilling).

Why useContext?

Without context:

<App>
  <Header user={user} />
  <Main user={user} />
</App>

With context:

• Data is stored in one place

• Any component can access it directly

What is Context?

Context provides a way to pass data through the component tree without using props.

Typical use cases:

• Theme (light/dark)

• Authentication

• Language settings

• Global user data

Basic Steps to Use useContext

1. Create Context

import { createContext } from "react";

export const UserContext = createContext();

2. Provide Context Value

Wrap components with a Provider.

import { UserContext } from "./UserContext";

function App() {
  const user = { name: "Alice" };

  return (
    <UserContext.Provider value={user}>
      <Dashboard />
    </UserContext.Provider>
  );
}

3. Consume Context with useContext

import { useContext } from "react";
import { UserContext } from "./UserContext";

function Dashboard() {
  const user = useContext(UserContext);

  return <h1>Welcome, {user.name}</h1>;
}

Using Context with State

function App() {
  const [theme, setTheme] = useState("light");

  return (
    <ThemeContext.Provider value={{ theme, setTheme }}>
      <Page />
    </ThemeContext.Provider>
  );
}

Consume it:

const { theme, setTheme } = useContext(ThemeContext);

Default Context Value

const ThemeContext = createContext("light");

Used when no Provider is found.

Updating Context Data

Context values update all consuming components.

<button onClick={() => setTheme("dark")}>
  Dark Mode
</button>

Common Mistakes

❌ Using context for everything
❌ Forgetting to wrap Provider
❌ Storing large, frequently changing data

When to Use useContext

✅ Good for:

• Global app settings

• Authentication data

• Theme and localization

❌ Avoid for:

• High-frequency updates

• Deeply complex state logic

Context vs Redux

Best Practices

• Keep context values small

• Split contexts by responsibility

• Memoize context values if needed

Key Points

• useContext avoids prop drilling

• Works with createContext

• Provider shares data

• All consumers re-render on change