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
.
Note: This feature is available in Web Workers
Instance properties
IDBIndex.isAutoLocale
Read only Non-standard Experimental-
Returns a boolean value indicating whether the index had a
locale
value ofauto
specified upon its creation (see theoptions
parameter toIDBObjectStore.createIndex()
.) IDBIndex.locale
Read only Non-standard Experimental-
Returns the locale of the index (for example
en-US
, orpl
) if it had alocale
value specified upon its creation (see theoptions
parameter toIDBObjectStore.createIndex()
.) IDBIndex.name
-
The name of this index.
IDBIndex.objectStore
Read only-
The name of the object store referenced by this index.
IDBIndex.keyPath
Read only-
The key path of this index. If null, this index is not auto-populated.
IDBIndex.multiEntry
Read only-
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. Iffalse
, then there is one record for each key that is an array. IDBIndex.unique
Read only-
If
true
, this index does not allow duplicate values for a key.
Instance methods
Inherits from: EventTarget
IDBIndex.count()
-
Returns an
IDBRequest
object, and in a separate thread, returns the number of records within a key range. IDBIndex.get()
-
Returns an
IDBRequest
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, ifkey
is anIDBKeyRange
. IDBIndex.getKey()
-
Returns an
IDBRequest
object, and, in a separate thread, finds either the given key or the primary key, ifkey
is anIDBKeyRange
. IDBIndex.getAll()
-
Returns an
IDBRequest
object, in a separate thread, finds all matching values in the referenced object store that correspond to the given key or are in range, ifkey
is anIDBKeyRange
. IDBIndex.getAllKeys()
-
Returns an
IDBRequest
object, in a separate thread, finds all matching keys in the referenced object store that correspond to the given key or are in range, ifkey
is anIDBKeyRange
. IDBIndex.openCursor()
-
Returns an
IDBRequest
object, and, in a separate thread, creates a cursor over the specified key range. IDBIndex.openKeyCursor()
-
Returns an
IDBRequest
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
— this works the same as opening a cursor directly on an ObjectStore
using IDBObjectStore.openCursor
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 IndexedDB-examples demo repo (View the example live.)
js
function displayDataByIndex() {
tableEntry.innerHTML = "";
const transaction = db.transaction(["contactsList"], "readonly");
const objectStore = transaction.objectStore("contactsList");
const myIndex = objectStore.index("lName");
myIndex.openCursor().onsuccess = (event) => {
const cursor = event.target.result;
if (cursor) {
const 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.");
}
};
}
Specifications
Specification |
---|
Indexed Database API 3.0 # index-interface |
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 the example live).