Smart To-Do List with LocalStorage

<div class="todo-app">
  <header class="app-header">
    <div class="header-icon"><i class="fas fa-check-double"></i></div>
    <div>
      <h1>TaskFlow</h1>
      <p class="subtitle">Stay organized and get things done</p>
    </div>
  </header>

  <form id="todo-form" class="todo-form" autocomplete="off">
    <div class="input-group">
      <input type="text" id="todo-input" placeholder="What needs to be done?" required autocomplete="off" spellcheck="false">
      <select id="todo-priority" title="Task Priority">
        <option value="normal">Normal</option>
        <option value="high">High</option>
        <option value="low">Low</option>
      </select>
      <button type="submit" id="add-btn" class="btn-primary" title="Add Task">
        <i class="fas fa-plus"></i> <span>Add</span>
      </button>
    </div>
  </form>

  <div class="controls-bar">
    <div class="filter-tabs">
      <button type="button" class="tab-btn active" data-filter="all">All</button>
      <button type="button" class="tab-btn" data-filter="active">Active</button>
      <button type="button" class="tab-btn" data-filter="completed">Completed</button>
    </div>
    <button type="button" id="clear-completed-btn" class="btn-clear">
      <i class="fas fa-trash-alt me-1"></i> Clear Completed
    </button>
  </div>

  <ul id="todo-list" class="todo-list">
    <!-- Tasks dynamically rendered here -->
  </ul>

  <footer class="app-footer">
    <span id="items-left">0 items left</span>
    <span class="storage-hint" id="storage-status"><i class="fas fa-database"></i> Storage Ready</span>
  </footer>
</div>

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}
body {
  background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
  color: #1e293b;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  overflow-x: hidden;
}
.todo-app {
  background: #ffffff;
  border-radius: 20px;
  width: 100%;
  max-width: 520px;
  box-shadow: 0 20px 40px -15px rgba(0, 0, 0, 0.4);
  padding: 24px;
  border: 1px solid rgba(255, 255, 255, 0.2);
}
.app-header {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 20px;
}
.header-icon {
  width: 46px;
  height: 46px;
  background: rgba(16, 185, 129, 0.12);
  color: #10b981;
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
  flex-shrink: 0;
}
.app-header h1 {
  color: #0f172a;
  font-size: 1.5rem;
  font-weight: 800;
  line-height: 1.1;
}
.subtitle {
  color: #64748b;
  font-size: 0.85rem;
  margin-top: 3px;
}
.todo-form .input-group {
  display: flex;
  gap: 8px;
  margin-bottom: 18px;
}
#todo-input {
  flex: 1;
  min-width: 0;
  padding: 11px 14px;
  border: 1.5px solid #cbd5e1;
  border-radius: 12px;
  font-size: 0.92rem;
  outline: none;
  transition: all 0.2s;
  background: #f8fafc;
}
#todo-input:focus {
  background: #ffffff;
  border-color: #10b981;
  box-shadow: 0 0 0 4px rgba(16, 185, 129, 0.15);
}
#todo-priority {
  padding: 0 10px;
  border: 1.5px solid #cbd5e1;
  border-radius: 12px;
  background: #f8fafc;
  color: #334155;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  outline: none;
  flex-shrink: 0;
  transition: border-color 0.2s;
}
#todo-priority:focus {
  border-color: #10b981;
}
.btn-primary {
  background: #10b981;
  color: #ffffff;
  border: none;
  padding: 11px 18px;
  border-radius: 12px;
  font-weight: 700;
  font-size: 0.92rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  flex-shrink: 0;
  box-shadow: 0 4px 12px rgba(16, 185, 129, 0.3);
  transition: all 0.2s;
}
.btn-primary:hover {
  background: #059669;
  transform: translateY(-1px);
}
.btn-primary:active {
  transform: translateY(0);
}
.controls-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid #f1f5f9;
  flex-wrap: wrap;
  gap: 10px;
}
.filter-tabs {
  display: flex;
  background: #f1f5f9;
  padding: 4px;
  border-radius: 10px;
  gap: 4px;
}
.tab-btn {
  background: transparent;
  border: none;
  padding: 6px 12px;
  font-size: 0.82rem;
  font-weight: 700;
  color: #64748b;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s;
}
.tab-btn.active {
  background: #ffffff;
  color: #0f172a;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.08);
}
.btn-clear {
  background: transparent;
  border: none;
  color: #ef4444;
  font-size: 0.82rem;
  cursor: pointer;
  font-weight: 600;
  transition: color 0.2s;
  padding: 4px 6px;
}
.btn-clear:hover {
  color: #b91c1c;
  text-decoration: underline;
}
.todo-list {
  list-style: none;
  max-height: 320px;
  overflow-y: auto;
  margin-bottom: 16px;
  padding-right: 2px;
}
.todo-item {
  display: flex;
  align-items: center;
  padding: 10px 12px;
  background: #f8fafc;
  border: 1px solid #e2e8f0;
  border-radius: 12px;
  margin-bottom: 8px;
  transition: all 0.25s ease;
  animation: slideDown 0.25s ease;
  gap: 8px;
}
@keyframes slideDown {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}
.todo-item:hover {
  background: #f1f5f9;
  border-color: #cbd5e1;
}
.todo-item.completed {
  background: #f8fafc;
  opacity: 0.65;
}
.todo-item.completed .todo-text {
  text-decoration: line-through;
  color: #94a3b8;
}
.checkbox-custom {
  width: 20px;
  height: 20px;
  border-radius: 6px;
  cursor: pointer;
  accent-color: #10b981;
  flex-shrink: 0;
}
.todo-text {
  flex: 1;
  min-width: 0;
  font-size: 0.92rem;
  font-weight: 500;
  color: #1e293b;
  word-break: break-word;
  overflow-wrap: break-word;
}
.priority-tag {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: 2px 7px;
  border-radius: 6px;
  flex-shrink: 0;
  letter-spacing: 0.4px;
}
.priority-high { background: #fee2e2; color: #dc2626; border: 1px solid #fecaca; }
.priority-normal { background: #e0f2fe; color: #0284c7; border: 1px solid #bae6fd; }
.priority-low { background: #f1f5f9; color: #64748b; border: 1px solid #e2e8f0; }
.delete-btn {
  background: transparent;
  border: none;
  color: #94a3b8;
  font-size: 0.95rem;
  cursor: pointer;
  transition: color 0.2s;
  padding: 6px;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.delete-btn:hover {
  color: #ef4444;
}
.empty-state {
  text-align: center;
  padding: 32px 10px;
  color: #94a3b8;
  font-size: 0.9rem;
}
.app-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: #64748b;
  font-weight: 500;
  border-top: 1px solid #f1f5f9;
  padding-top: 12px;
  flex-wrap: wrap;
  gap: 6px;
}
.storage-hint {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  color: #10b981;
  font-size: 0.76rem;
  font-weight: 600;
}

/* Mobile Responsiveness */
@media (max-width: 520px) {
  body {
    padding: 10px 8px;
    align-items: flex-start;
  }
  .todo-app {
    padding: 16px 12px;
    border-radius: 16px;
  }
  .app-header {
    gap: 10px;
    margin-bottom: 14px;
  }
  .header-icon {
    width: 38px;
    height: 38px;
    font-size: 1.1rem;
    border-radius: 10px;
  }
  .app-header h1 {
    font-size: 1.3rem;
  }
  .subtitle {
    font-size: 0.78rem;
  }
  .todo-form .input-group {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 8px;
  }
  #todo-input {
    grid-column: 1 / -1;
    width: 100%;
    padding: 10px 12px;
    font-size: 0.88rem;
  }
  #todo-priority {
    height: 38px;
    font-size: 0.82rem;
  }
  .btn-primary {
    height: 38px;
    padding: 0 14px;
    font-size: 0.85rem;
  }
  .controls-bar {
    flex-direction: column;
    align-items: stretch;
    gap: 8px;
    margin-bottom: 12px;
  }
  .filter-tabs {
    width: 100%;
    display: flex;
  }
  .tab-btn {
    flex: 1;
    text-align: center;
    padding: 6px 4px;
    font-size: 0.76rem;
  }
  .btn-clear {
    width: 100%;
    text-align: center;
    padding: 4px;
    font-size: 0.78rem;
  }
  .todo-item {
    padding: 8px 10px;
    gap: 6px;
  }
  .todo-text {
    font-size: 0.86rem;
  }
  .priority-tag {
    font-size: 0.65rem;
    padding: 2px 5px;
  }
  .delete-btn {
    padding: 4px;
    font-size: 0.88rem;
  }
  .app-footer {
    flex-direction: column;
    align-items: center;
    gap: 4px;
    text-align: center;
  }
}

// Storage Safe Helper
const STORAGE_KEY = 'taskflow_todos_v2';

function loadTodos() {
  try {
    const data = localStorage.getItem(STORAGE_KEY);
    if (data) {
      const parsed = JSON.parse(data);
      if (Array.isArray(parsed) && parsed.length > 0) return parsed;
    }
  } catch (e) {
    console.warn('LocalStorage unavailable in sandbox, using memory state:', e);
  }
  return [
    { id: 1, text: 'Learn JavaScript basics & DOM manipulation', priority: 'high', completed: true },
    { id: 2, text: 'Build interactive beginner projects', priority: 'normal', completed: false },
    { id: 3, text: 'Master state management and event listeners', priority: 'low', completed: false }
  ];
}

function saveTodos(data) {
  try {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(data));
  } catch (e) {}
}

let todos = loadTodos();
let currentFilter = 'all';

// DOM Elements
const form = document.getElementById('todo-form');
const input = document.getElementById('todo-input');
const prioritySelect = document.getElementById('todo-priority');
const addBtn = document.getElementById('add-btn');
const list = document.getElementById('todo-list');
const itemsLeft = document.getElementById('items-left');
const filterBtns = document.querySelectorAll('.tab-btn');
const clearCompletedBtn = document.getElementById('clear-completed-btn');

function escapeHtml(text) {
  const div = document.createElement('div');
  div.textContent = text;
  return div.innerHTML;
}

function renderTodos() {
  list.innerHTML = '';

  const filtered = todos.filter(t => {
    if (currentFilter === 'active') return !t.completed;
    if (currentFilter === 'completed') return t.completed;
    return true;
  });

  if (filtered.length === 0) {
    list.innerHTML = `
      <div class="empty-state">
        <i class="far fa-clipboard" style="font-size:2.2rem;margin-bottom:8px;display:block;color:#cbd5e1"></i>
        No tasks found in this filter.
      </div>
    `;
  } else {
    filtered.forEach(todo => {
      const li = document.createElement('li');
      li.className = `todo-item ${todo.completed ? 'completed' : ''}`;
      li.dataset.id = todo.id;

      li.innerHTML = `
        <input type="checkbox" class="checkbox-custom" ${todo.completed ? 'checked' : ''} aria-label="Mark task completed">
        <span class="todo-text">${escapeHtml(todo.text)}</span>
        <span class="priority-tag priority-${todo.priority}">${todo.priority}</span>
        <button type="button" class="delete-btn" title="Delete Task"><i class="fas fa-trash-alt"></i></button>
      `;

      list.appendChild(li);
    });
  }

  // Update active counter
  const activeCount = todos.filter(t => !t.completed).length;
  itemsLeft.textContent = `${activeCount} item${activeCount === 1 ? '' : 's'} left`;
}

function addTodo() {
  const text = input.value.trim();
  if (!text) {
    input.focus();
    return;
  }

  const newTodo = {
    id: Date.now(),
    text: text,
    priority: prioritySelect.value || 'normal',
    completed: false
  };

  todos.unshift(newTodo);
  saveTodos(todos);
  renderTodos();
  input.value = '';
  input.focus();
}

// Add task on Form Submit
form.addEventListener('submit', (e) => {
  e.preventDefault();
  addTodo();
});

// Add task on direct button click
addBtn.addEventListener('click', (e) => {
  e.preventDefault();
  addTodo();
});

// Add task on Enter key inside input
input.addEventListener('keydown', (e) => {
  if (e.key === 'Enter') {
    e.preventDefault();
    addTodo();
  }
});

// Toggle complete & delete using event delegation
list.addEventListener('click', (e) => {
  const item = e.target.closest('.todo-item');
  if (!item) return;
  const id = Number(item.dataset.id);

  if (e.target.classList.contains('checkbox-custom')) {
    todos = todos.map(t => t.id === id ? { ...t, completed: !t.completed } : t);
    saveTodos(todos);
    renderTodos();
  } else if (e.target.closest('.delete-btn')) {
    todos = todos.filter(t => t.id !== id);
    saveTodos(todos);
    renderTodos();
  }
});

// Filter Tabs
filterBtns.forEach(btn => {
  btn.addEventListener('click', () => {
    filterBtns.forEach(b => b.classList.remove('active'));
    btn.classList.add('active');
    currentFilter = btn.dataset.filter;
    renderTodos();
  });
});

// Clear Completed
clearCompletedBtn.addEventListener('click', () => {
  todos = todos.filter(t => !t.completed);
  saveTodos(todos);
  renderTodos();
});

// Initial render
renderTodos();