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awesome-copilot/plugins/react18-upgrade/skills/react18-legacy-context/references/context-file-template.md
2026-04-09 06:26:21 +00:00

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# Context File Template
Standard template for a new context module. Copy and fill in the name.
## Template
```jsx
// src/contexts/[Name]Context.js
import React from 'react';
// ─── 1. Default Value ───────────────────────────────────────────────────────
// Shape must match what the provider will pass as `value`
// Used when a consumer renders outside any provider (edge case protection)
const defaultValue = {
// fill in the shape
};
// ─── 2. Create Context ──────────────────────────────────────────────────────
export const [Name]Context = React.createContext(defaultValue);
// ─── 3. Display Name (for React DevTools) ───────────────────────────────────
[Name]Context.displayName = '[Name]Context';
// ─── 4. Optional: Custom Hook (strongly recommended) ────────────────────────
// Provides a clean import path and a helpful error if used outside provider
export function use[Name]() {
const context = React.useContext([Name]Context);
if (context === defaultValue) {
// Only throw if defaultValue is a sentinel - skip if a real default makes sense
// throw new Error('use[Name] must be used inside a [Name]Provider');
}
return context;
}
```
## Filled Example - AuthContext
```jsx
// src/contexts/AuthContext.js
import React from 'react';
const defaultValue = {
user: null,
isAuthenticated: false,
login: () => Promise.resolve(),
logout: () => {},
};
export const AuthContext = React.createContext(defaultValue);
AuthContext.displayName = 'AuthContext';
export function useAuth() {
return React.useContext(AuthContext);
}
```
## Filled Example - ThemeContext
```jsx
// src/contexts/ThemeContext.js
import React from 'react';
const defaultValue = {
theme: 'light',
toggleTheme: () => {},
};
export const ThemeContext = React.createContext(defaultValue);
ThemeContext.displayName = 'ThemeContext';
export function useTheme() {
return React.useContext(ThemeContext);
}
```
## Where to Put Context Files
```
src/
contexts/ ← preferred: dedicated folder
AuthContext.js
ThemeContext.js
```
Alternative acceptable locations:
```
src/context/ ← singular is also fine
src/store/contexts/ ← if co-located with state management
```
Do NOT put context files inside a component folder - contexts are cross-cutting and shouldn't be owned by any one component.
## Provider Placement in the App
Context providers wrap the components that need access. Place as low in the tree as possible, not always at root:
```jsx
// App.js
import { ThemeProvider } from './ThemeProvider';
import { AuthProvider } from './AuthProvider';
function App() {
return (
// Auth wraps everything - login state is needed everywhere
<AuthProvider>
{/* Theme wraps only the UI shell - not needed in pure data providers */}
<ThemeProvider>
<Router>
<AppShell />
</Router>
</ThemeProvider>
</AuthProvider>
);
}
```