IDBObjectStore.clear() - Web APIs 编辑

The clear() method of the IDBObjectStore interface creates and immediately returns an IDBRequest object, and clears this object store in a separate thread. This is for deleting all the current data out of an object store.

Clearing an object store consists of removing all records from the object store and removing all records in indexes that reference the object store. To remove only some of the records in a store, use IDBObjectStore.delete passing a key or IDBKeyRange.

Note:

Syntax

var request = objectStore.clear();

Returns

An IDBRequest object on which subsequent events related to this operation are fired.

Exceptions

This method may raise a DOMException of one of the following types:

Example

In the following code snippet, we open a read/write transaction on our database and clear all the current data out of the object store using clear(). For a full working example, see our To-do Notifications app (view example live.)

// Let us open our database
var DBOpenRequest = window.indexedDB.open("toDoList", 4);

DBOpenRequest.onsuccess = function(event) {
  note.innerHTML += '<li>Database initialised.</li>';

  // store the result of opening the database in the db variable.
  // This is used a lot below
  db = DBOpenRequest.result;

  // Clear all the data form the object store
  clearData();
};

function clearData() {
  // open a read/write db transaction, ready for clearing the data
  var transaction = db.transaction(["toDoList"], "readwrite");

  // report on the success of the transaction completing, when everything is done
  transaction.oncomplete = function(event) {
    note.innerHTML += '<li>Transaction completed.</li>';
  };

  transaction.onerror = function(event) {
    note.innerHTML += '<li>Transaction not opened due to error: ' + transaction.error + '</li>';
  };

  // create an object store on the transaction
  var objectStore = transaction.objectStore("toDoList");

  // Make a request to clear all the data out of the object store
  var objectStoreRequest = objectStore.clear();

  objectStoreRequest.onsuccess = function(event) {
    // report the success of our request
    note.innerHTML += '<li>Request successful.</li>';
  };
};

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Using IndexedDB
• Starting transactions: IDBDatabase
• Using transactions: IDBTransaction
• Setting a range of keys: IDBKeyRange
• Retrieving and making changes to your data: IDBObjectStore
• Using cursors: IDBCursor
• Reference example: To-do Notifications (view example live.)