HTML Code
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>IndexedDB check then delete</title>
  <style>
    body { font-family: system-ui, sans-serif; margin: 1.5rem; line-height: 1.5; }
    button { margin-right: 0.5rem; margin-bottom: 0.5rem; padding: 0.5rem 0.9rem; cursor: pointer; }
    #status { margin-top: 1rem; }
  </style>
</head>
<body>
  <h1>Check before delete</h1>
  <p>Seed id 1, try deleting id 1 and a missing id 99.</p>

  <button type="button" id="seedBtn" disabled>Seed id 1</button>
  <button type="button" id="del1Btn" disabled>Delete id 1</button>
  <button type="button" id="del99Btn" disabled>Delete id 99</button>

  <p id="status">Opening database&hellip;</p>

  <script>
    var statusEl = document.getElementById('status');
    var db;

    function deleteContact(id) {
      var tx = db.transaction(['contacts'], 'readwrite');
      var store = tx.objectStore('contacts');
      var found = false;

      store.get(id).onsuccess = function (event) {
        if (!event.target.result) {
          statusEl.textContent = 'Contact ' + id + ' not found.';
          return;
        }
        found = true;
        store.delete(id);
      };

      tx.oncomplete = function () {
        if (found) {
          statusEl.textContent = 'Deleted contact id ' + id + '.';
        }
      };
    }

    var openReq = indexedDB.open('tryitDeleteCheck', 1);

    openReq.onupgradeneeded = function (event) {
      event.target.result.createObjectStore('contacts', { keyPath: 'id' });
    };

    openReq.onsuccess = function (event) {
      db = event.target.result;
      statusEl.textContent = 'Ready.';
      ['seedBtn', 'del1Btn', 'del99Btn'].forEach(function (id) {
        document.getElementById(id).disabled = false;
      });
    };

    document.getElementById('seedBtn').addEventListener('click', function () {
      var tx = db.transaction(['contacts'], 'readwrite');
      tx.objectStore('contacts').put({ id: 1, name: 'Alex Rivera' });
      tx.oncomplete = function () {
        statusEl.textContent = 'Seeded contact id 1.';
      };
    });

    document.getElementById('del1Btn').addEventListener('click', function () {
      deleteContact(1);
    });

    document.getElementById('del99Btn').addEventListener('click', function () {
      deleteContact(99);
    });
  </script>
</body>
</html>
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IndexedDB Delete — Check Then Delete
