frame-testing-indexed-db-storage.html

<!DOCTYPE html>
<script>
  const openRequest = window.indexedDB.open("test-database");
  openRequest.onerror = (event) => window.parent.postMessage('not able to open database', '*');
  // upgrade on the first access
  openRequest.onupgradeneeded = (event) => {
    const database = event.target.result;
    let objectStore;
    try {
      // will fail if object store with this name already exists
      objectStore = database.createObjectStore("test-store");
    } catch (e) {
      const transaction = event.target.transaction;
      objectStore = transaction.objectStore('test-store');
    }
    getItem(objectStore);
    objectStore.add("test-data", "test-key");
  };
  // success on the second access
  openRequest.onsuccess = (event) => {
    const database = event.target.result;
    const transaction = database.transaction(['test-store'],'readwrite');
    const objectStore = transaction.objectStore("test-store");

    getItem(objectStore);
  };

  function getItem(objectStore) {
    const getRequest = objectStore.get("test-key");
    getRequest.onsuccess = event => window.parent.postMessage("item value: " + getRequest.result, '*');
    getRequest.onerror = event => window.parent.postMessage("get failed", '*');
  }
</script>

chromium/third_party/blink/web_tests/http/tests/inspector-protocol/resources/frame-testing-indexed-db-storage.html