Frontend State React Context

When to use this skill

• Avoiding prop drilling
• Sharing theme/locale
• Authentication state
• Small global state needs

Workflow

• ] Create context with createContext
• ] Create provider component
• ] Create custom hook for consumption
• ] Split contexts to avoid re-renders
• ] Memoize provider value

Instructions

Basic Pattern

typescript
import { createContext, useContext, useState } from 'react';

interface ThemeContextType {
  theme: 'light' | 'dark';
  toggleTheme: () => void;
}

const ThemeContext = createContext<ThemeContextType | null>(null);

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setTheme] = useState<'light' | 'dark'>('light');

  const value = useMemo(() => ({
    theme,
    toggleTheme: () => setTheme(t => t === 'light' ? 'dark' : 'light')
  }), [theme]);

  return (
    <ThemeContext.Provider value={value}>
      {children}
    </ThemeContext.Provider>
  );
}

export function useTheme() {
  const context = useContext(ThemeContext);
  if (!context) throw new Error('useTheme must be used within ThemeProvider');
  return context;
}

Resources

• Memoize provider value
• Split contexts by concern
• Not ideal for frequently changing state