Type-Safe localStorage

Raw localStorage calls are error-prone: no type safety, manual JSON.parse everywhere, and silent failures when storage is full or disabled. This wrapper fixes all of that.

function getItem<T>(key: string): T | null {
  try {
    const item = localStorage.getItem(key);
    return item ? (JSON.parse(item) as T) : null;
  } catch {
    return null;
  }
}

function setItem<T>(key: string, value: T): void {
  try {
    localStorage.setItem(key, JSON.stringify(value));
  } catch {
    console.warn(`Failed to save "${key}" to localStorage`);
  }
}

function removeItem(key: string): void {
  localStorage.removeItem(key);
}

Usage

interface UserPreferences {
  theme: 'light' | 'dark';
  language: string;
  fontSize: number;
}

// Set
setItem<UserPreferences>('preferences', {
  theme: 'dark',
  language: 'en',
  fontSize: 16
});

// Get — returns UserPreferences | null
const prefs = getItem<UserPreferences>('preferences');

// Remove
removeItem('preferences');

With Expiry

Store values that automatically expire after a given duration:

interface StorageItem<T> {
  value: T;
  expiry: number;
}

function setItemWithExpiry<T>(key: string, value: T, ttlMs: number): void {
  const item: StorageItem<T> = {
    value,
    expiry: Date.now() + ttlMs
  };

  setItem(key, item);
}

function getItemWithExpiry<T>(key: string): T | null {
  const item = getItem<StorageItem<T>>(key);

  if (!item) return null;

  if (Date.now() > item.expiry) {
    removeItem(key);
    return null;
  }

  return item.value;
}

// Cache API response for 5 minutes
setItemWithExpiry('user-profile', userData, 5 * 60 * 1000);

// Returns null after expiry
const cached = getItemWithExpiry<UserData>('user-profile');