IDBIndex

IDBIndex interface of the IndexedDB API provides asynchronous access to an index in a database. An index is a kind of object store for looking up records in another object store, called the referenced object store. You use this interface to retrieve data.

You can retrieve records in an object store through the primary key or by using an index. An index lets you look up records in an object store using properties of the values in the object stores records other than the primary key

The index is a persistent key-value storage where the value part of its records is the key part of a record in the referenced object store. The records in an index are automatically populated whenever records in the referenced object store are inserted, updated, or deleted. Each record in an index can point to only one record in its referenced object store, but several indexes can reference the same object store. When the object store changes, all indexes that refers to the object store are automatically updated.

You can grab a set of keys within a range. To learn more, see IDBKeyRange (en-US).

Примечание: Эта возможность доступна в Web Workers.

Properties

IDBIndex.isAutoLocale (en-US) Только для чтения Это API не было стандартизировано.
Returns a Boolean (en-US) indicating whether the index had a locale value of auto specified upon its creation (see createIndex()'s optionalParameters.)
IDBIndex.locale Только для чтения Это API не было стандартизировано.
Returns the locale of the index (for example en-US, or pl) if it had a locale value specified upon its creation (see createIndex()'s optionalParameters.)
IDBIndex.name (en-US)
The name of this index.
IDBIndex.objectStore (en-US) Только для чтения
The name of the object store referenced by this index.
IDBIndex.keyPath (en-US) Только для чтения
The key path of this index. If null, this index is not auto-populated.
IDBIndex.multiEntry (en-US) Только для чтения
Affects how the index behaves when the result of evaluating the index's key path yields an array. If true, there is one record in the index for each item in an array of keys. If false, then there is one record for each key that is an array.
IDBIndex.unique (en-US) Только для чтения
If true, this index does not allow duplicate values for a key.

Methods

Inherits from: EventTarget

IDBIndex.count() (en-US)
Returns an IDBRequest (en-US) object, and in a separate thread, returns the number of records within a key range.
IDBIndex.get() (en-US)
Returns an IDBRequest (en-US) object, and, in a separate thread, finds either the value in the referenced object store that corresponds to the given key or the first corresponding value, if key is an IDBKeyRange (en-US).
IDBIndex.getKey() (en-US)
Returns an IDBRequest (en-US) object, and, in a separate thread, finds either the given key or the primary key, if key is an IDBKeyRange (en-US).
IDBIndex.getAll() (en-US)
Returns an IDBRequest (en-US) object, in a separate thread, finds all matching values in the referenced object store that correspond to the given key or are in range, if key is an IDBKeyRange (en-US).
IDBIndex.getAllKeys() (en-US)
Returns an IDBRequest (en-US) object, in a separate thread, finds all matching keys in the referenced object store that correspond to the given key or are in range, if key is an IDBKeyRange (en-US).
IDBIndex.openCursor() (en-US)
Returns an IDBRequest (en-US) object, and, in a separate thread, creates a cursor over the specified key range.
IDBIndex.openKeyCursor() (en-US)
Returns an IDBRequest (en-US) object, and, in a separate thread, creates a cursor over the specified key range, as arranged by this index.

Example

In the following example we open a transaction and an object store, then get the index lName from a simple contacts database. We then open a basic cursor on the index using IDBIndex.openCursor (en-US) — this works the same as opening a cursor directly on an ObjectStore using IDBObjectStore.openCursor (en-US) except that the returned records are sorted based on the index, not the primary key.

Finally, we iterate through each record, and insert the data into an HTML table. For a complete working example, see our IDBIndex-example demo repo (View the example live.)

function displayDataByIndex() {
  tableEntry.innerHTML = '';
  var transaction = db.transaction(['contactsList'], 'readonly');
  var objectStore = transaction.objectStore('contactsList');

  var myIndex = objectStore.index('lName');
  myIndex.openCursor().onsuccess = function(event) {
    var cursor = event.target.result;
    if(cursor) {
      var tableRow = document.createElement('tr');
      tableRow.innerHTML =   '<td>' + cursor.value.id + '</td>'
                           + '<td>' + cursor.value.lName + '</td>'
                           + '<td>' + cursor.value.fName + '</td>'
                           + '<td>' + cursor.value.jTitle + '</td>'
                           + '<td>' + cursor.value.company + '</td>'
                           + '<td>' + cursor.value.eMail + '</td>'
                           + '<td>' + cursor.value.phone + '</td>'
                           + '<td>' + cursor.value.age + '</td>';
      tableEntry.appendChild(tableRow);

      cursor.continue();
    } else {
      console.log('Entries all displayed.');
    }
  };
};

Specification

Specification Status Comment
Indexed Database API 2.0
Определение 'IDBIndex' в этой спецификации.
Рекомендация  
Indexed Database API 2.0
Определение 'IDBIndex' в этой спецификации.
Рекомендация  

Browser compatibility

BCD tables only load in the browser

See also