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  <meta charset="UTF-8">
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  <title>Web SQL — complete demo</title>
  <style>
    body {
      font-family: system-ui, sans-serif;
      margin: 0;
      padding: 1.5rem;
      background: #f8fafc;
      color: #334155;
      line-height: 1.6;
    }
    h1 { margin: 0 0 0.5rem; font-size: 1.25rem; color: #0f172a; }
    p { margin: 0 0 1rem; max-width: 460px; }
    .btn-row { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-bottom: 1rem; }
    button {
      padding: 0.55rem 1rem;
      font-size: 0.9375rem;
      background: #2563eb;
      color: #fff;
      border: none;
      border-radius: 8px;
      cursor: pointer;
    }
    button.secondary { background: #7c3aed; }
    button:hover { filter: brightness(1.08); }
    #status {
      margin-bottom: 0.75rem;
      padding: 0.75rem 1rem;
      max-width: 460px;
      background: #fff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      font-size: 0.875rem;
    }
    #status.ok { border-left: 4px solid #22c55e; }
    #status.err { border-left: 4px solid #ef4444; }
    ul {
      margin: 0;
      padding-left: 1.25rem;
      max-width: 460px;
      font-size: 0.875rem;
    }
    li { margin-bottom: 0.35rem; }
    .hint {
      margin-top: 1rem;
      font-size: 0.8125rem;
      color: #64748b;
      max-width: 460px;
    }
  </style>
</head>
<body>
  <h1>Web SQL mini address book</h1>
  <p>Add contacts and list them — all stored in a client-side SQLite database.</p>

  <div class="btn-row">
    <button type="button" id="addBtn">Add random contact</button>
    <button type="button" id="listBtn" class="secondary">List all contacts</button>
  </div>

  <p id="status">Initializing database&hellip;</p>
  <ul id="list"></ul>
  <p class="hint">Each click runs SQL inside <code>db.transaction()</code>. Errors roll back the transaction.</p>

  <script>
    var statusEl = document.getElementById('status');
    var listEl = document.getElementById('list');
    var names = ['Sam Lee', 'Jordan Kim', 'Taylor Brooks', 'Casey Morgan', 'Riley Chen'];

    if (!window.openDatabase) {
      statusEl.textContent = 'Web SQL is not supported in this browser.';
      statusEl.className = 'err';
    } else {
      var db = openDatabase('addressBook', '1.0', 'Address Book', 2 * 1024 * 1024);

      db.transaction(function (tx) {
        tx.executeSql(
          'CREATE TABLE IF NOT EXISTS contacts (id INTEGER PRIMARY KEY, name TEXT)'
        );
      }, function (error) {
        statusEl.textContent = 'Setup failed: ' + error.message;
        statusEl.className = 'err';
      }, function () {
        statusEl.textContent = 'Database ready. Add or list contacts.';
        statusEl.className = 'ok';
      });

      document.getElementById('addBtn').addEventListener('click', function () {
        var id = Date.now();
        var name = names[Math.floor(Math.random() * names.length)];

        db.transaction(function (tx) {
          tx.executeSql(
            'INSERT INTO contacts (id, name) VALUES (?, ?)',
            [id, name],
            function () {
              statusEl.textContent = 'Added "' + name + '" (id ' + id + ')';
              statusEl.className = 'ok';
            },
            function (tx, error) {
              statusEl.textContent = 'Insert failed: ' + error.message;
              statusEl.className = 'err';
              return true;
            }
          );
        });
      });

      document.getElementById('listBtn').addEventListener('click', function () {
        db.transaction(function (tx) {
          tx.executeSql(
            'SELECT * FROM contacts ORDER BY name',
            [],
            function (tx, results) {
              listEl.innerHTML = '';
              if (!results.rows.length) {
                listEl.innerHTML = '<li><em>No contacts yet.</em></li>';
              } else {
                for (var i = 0; i < results.rows.length; i++) {
                  var row = results.rows.item(i);
                  var li = document.createElement('li');
                  li.textContent = row.name + ' (id ' + row.id + ')';
                  listEl.appendChild(li);
                }
              }
              statusEl.textContent = 'Showing ' + results.rows.length + ' contact(s).';
              statusEl.className = 'ok';
            },
            function (tx, error) {
              statusEl.textContent = 'Select failed: ' + error.message;
              statusEl.className = 'err';
              return true;
            }
          );
        });
      });
    }
  </script>
</body>
</html>
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Web SQL — Complete Add & List Demo
