React Snippets

Modern React patterns and hooks

useState Hook

tsx

Manage component state with useState

import { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>
        Increment
      </button>
    </div>
  );
}

useEffect Hook

tsx

Handle side effects in components

import { useEffect, useState } from 'react';

function UserProfile({ userId }) {
  const [user, setUser] = useState(null);

  useEffect(() => {
    async function fetchUser() {
      const response = await fetch(`/api/users/${userId}`);
      const data = await response.json();
      setUser(data);
    }

    fetchUser();
  }, [userId]); // Re-run when userId changes

  if (!user) return <div>Loading...</div>;

  return <div>{user.name}</div>;
}

Custom Hook

tsx

Create reusable custom hooks

import { useState, useEffect } from 'react';

function useLocalStorage(key, initialValue) {
  // Get stored value
  const [storedValue, setStoredValue] = useState(() => {
    try {
      const item = window.localStorage.getItem(key);
      return item ? JSON.parse(item) : initialValue;
    } catch (error) {
      return initialValue;
    }
  });

  // Update stored value
  const setValue = (value) => {
    try {
      setStoredValue(value);
      window.localStorage.setItem(key, JSON.stringify(value));
    } catch (error) {
      console.error(error);
    }
  };

  return [storedValue, setValue];
}

Context API

tsx

Share state between components

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

// Create context
const ThemeContext = createContext();

// Provider component
export function ThemeProvider({ children }) {
  const [theme, setTheme] = useState('light');

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

// Use context in components
function ThemedButton() {
  const { theme, setTheme } = useContext(ThemeContext);

  return (
    <button onClick={() => setTheme(theme === 'light' ? 'dark' : 'light')}>
      Current theme: {theme}
    </button>
  );
}