IDBOpenDBRequest: blocked event - Web APIs 编辑

The blocked handler is executed when an open connection to a database is blocking a versionchange transaction on the same database.

Examples

Using addEventListener():

// Open the database
const DBOpenRequest = window.indexedDB.open('toDoList', 4);

DBOpenRequest.onupgradeneeded = (event) => {
  const db = event.target.result;

  db.onerror = () => {
    console.log('Error creating database');
  };

  // Create an objectStore for this database
  var objectStore = db.createObjectStore('toDoList', { keyPath: 'taskTitle' });

  // define what data items the objectStore will contain
  objectStore.createIndex('hours', 'hours', { unique: false });
  objectStore.createIndex('minutes', 'minutes', { unique: false });
  objectStore.createIndex('day', 'day', { unique: false });
  objectStore.createIndex('month', 'month', { unique: false });
  objectStore.createIndex('year', 'year', { unique: false });
};

DBOpenRequest.onsuccess = (event) => {
  // Let's try to open the same database with a higher revision version
  const req2 = indexedDB.open('toDoList', 5);

  // In this case the onblocked handler will be executed
  req2.addEventListener('blocked', () => {
    console.log('Request was blocked');
  });

};

Using the onblocked property:

// Open the database
const DBOpenRequest = window.indexedDB.open('toDoList', 4);

DBOpenRequest.onupgradeneeded = (event) => {
  const db = event.target.result;

  db.onerror = () => {
    console.log('Error creating database');
  };

  // Create an objectStore for this database
  var objectStore = db.createObjectStore('toDoList', { keyPath: 'taskTitle' });

  // define what data items the objectStore will contain
  objectStore.createIndex('hours', 'hours', { unique: false });
  objectStore.createIndex('minutes', 'minutes', { unique: false });
  objectStore.createIndex('day', 'day', { unique: false });
  objectStore.createIndex('month', 'month', { unique: false });
  objectStore.createIndex('year', 'year', { unique: false });
};

DBOpenRequest.onsuccess = (event) => {
  // Let's try to open the same database with a higher revision version
  const req2 = indexedDB.open('toDoList', 5);

  // In this case the onblocked handler will be executed
  req2.onblocked = () => {
    console.log('Request was blocked');
  };

};

Browser compatibility

BCD tables only load in the browser

See also

• Using IndexedDB
• onblocked event handler property