// 獲取字符串
const username = localStorage.getItem('username');
console.log(username); // 輸出: john_doe

// 獲取數(shù)字（需要轉(zhuǎn)換回?cái)?shù)字類型）
const age = parseInt(localStorage.getItem('age'), 10);
console.log(age); // 輸出: 30

// 獲取對(duì)象（需要解析JSON字符串）
const storedUser = JSON.parse(localStorage.getItem('user'));
console.log(storedUser.name); // 輸出: John

const nonExistent = localStorage.getItem('non_existent_key');
console.log(nonExistent); // 輸出: null

localStorage.removeItem('username');

localStorage.clear();

if (typeof(Storage) !== 'undefined') {
  // 支持localStorage
  localStorage.setItem('test', 'support');
} else {
  // 不支持localStorage
  console.error('您的瀏覽器不支持localStorage');
}

// 存儲(chǔ)數(shù)據(jù)
function saveToLocalStorage(key, value) {
  try {
    const serializedValue = typeof value === 'object' ? JSON.stringify(value) : value;
    localStorage.setItem(key, serializedValue);
  } catch (error) {
    console.error('保存到localStorage失敗:', error);
  }
}

// 獲取數(shù)據(jù)
function getFromLocalStorage(key) {
  try {
    const value = localStorage.getItem(key);
    if (value === null) return null;
    
    try {
      return JSON.parse(value);
    } catch (e) {
      return value; // 如果不是JSON字符串，返回原始值
    }
  } catch (error) {
    console.error('從localStorage獲取數(shù)據(jù)失敗:', error);
    return null;
  }
}

// 使用示例
saveToLocalStorage('theme', 'dark');
saveToLocalStorage('settings', { fontSize: 16, color: 'blue' });

console.log(getFromLocalStorage('theme')); // 輸出: dark
console.log(getFromLocalStorage('settings')); // 輸出: { fontSize: 16, color: 'blue' }

window.addEventListener('storage', (event) => {
  console.log('Storage事件觸發(fā):', event);
  console.log('鍵:', event.key);
  console.log('舊值:', event.oldValue);
  console.log('新值:', event.newValue);
  console.log('URL:', event.url);
});

// 保存主題偏好
function setTheme(theme) {
  localStorage.setItem('theme', theme);
  document.documentElement.className = theme; // 應(yīng)用主題
}

// 獲取主題偏好
function getTheme() {
  const theme = localStorage.getItem('theme') || 'light'; // 默認(rèn)淺色主題
  document.documentElement.className = theme;
  return theme;
}

// 初始化
getTheme();

// 添加商品到購物車
function addToCart(productId, quantity) {
  let cart = getFromLocalStorage('cart') || {};
  
  if (cart[productId]) {
    cart[productId] += quantity;
  } else {
    cart[productId] = quantity;
  }
  
  saveToLocalStorage('cart', cart);
}

// 從購物車移除商品
function removeFromCart(productId) {
  let cart = getFromLocalStorage('cart') || {};
  
  if (cart[productId]) {
    delete cart[productId];
    saveToLocalStorage('cart', cart);
  }
}

// 獲取購物車商品數(shù)量
function getCartCount() {
  const cart = getFromLocalStorage('cart') || {};
  return Object.values(cart).reduce((total, quantity) => total + quantity, 0);
}