IDBObjectStore: createIndex() method
The createIndex()
method of the
IDBObjectStore
interface creates and returns a new
IDBIndex
object in the connected database. It creates a new
field/column defining a new data point for each database record to contain.
Bear in mind that IndexedDB indexes can contain any JavaScript data type; IndexedDB uses the structured clone algorithm to serialize stored objects, which allows for storage of simple and complex objects.
Note that this method must be called only from a VersionChange
transaction
mode callback.
Note: This feature is available in Web Workers
Syntax
js
createIndex(indexName, keyPath)
createIndex(indexName, keyPath, options)
Parameters
indexName
-
The name of the index to create. Note that it is possible to create an index with an empty name.
keyPath
-
The key path for the index to use. Note that it is possible to create an index with an empty
keyPath
, and also to pass in a sequence (array) as akeyPath
. options
Optional-
An object which can include the following properties:
unique
-
If
true
, the index will not allow duplicate values for a single key. Defaults tofalse
. multiEntry
-
If
true
, the index will add an entry in the index for each array element when thekeyPath
resolves to an array. Iffalse
, it will add one single entry containing the array. Defaults tofalse
. locale
Non-standard-
Currently Firefox-only (43+), this allows you to specify a locale for the index. Any sorting operations performed on the data via key ranges will then obey sorting rules of that locale (see locale-aware sorting). You can specify its value in one of three ways:
string
: A string containing a specific locale code, e.g.en-US
, orpl
.auto
: The platform default locale will be used (may be changed by user agent settings).null
orundefined
: If no locale is specified, normal JavaScript sorting will be used — not locale-aware.
Return value
An IDBIndex
object: the newly created index.
Exceptions
This method may raise a DOMException
of one of the following types:
ConstraintError
DOMException
-
Thrown if an index with the same name already exists in the database. Index names are case-sensitive.
InvalidAccessError
DOMException
-
Thrown if the provided key path is a sequence, and
multiEntry
is set totrue
in theobjectParameters
object. InvalidStateError
DOMException
-
Thrown if:
- The method was not called from a
versionchange
transaction mode callback, i.e. from inside aonupgradeneeded
handler. - The object store has been deleted.
- The method was not called from a
SyntaxError
DOMException
-
Thrown if the provided
keyPath
is not a valid key path. TransactionInactiveError
DOMException
-
Thrown if the transaction this
IDBObjectStore
belongs to is not active (e.g. has been deleted or removed.) In Firefox previous to version 41, anInvalidStateError
was raised in this case as well, which was misleading; this has now been fixed (see Webkit bug 1176165.)
Examples
In the following example you can see
the onupgradeneeded
handler being used to update the
database structure if a database with a higher version number is loaded.
createIndex()
is used to create new indexes on the object store. For a
full working example, see our To-do Notifications app (view example live).
js
let db;
// Let us open our database
const DBOpenRequest = window.indexedDB.open("toDoList", 4);
// Two event handlers for opening the database.
DBOpenRequest.onerror = (event) => {
note.innerHTML += "<li>Error loading database.</li>";
};
DBOpenRequest.onsuccess = (event) => {
note.innerHTML += "<li>Database initialized.</li>";
// store the result of opening the database in the db variable.
// This is used a lot below.
db = request.result;
// Run the displayData() function to populate the task list with
// all the to-do list data already in the IDB
displayData();
};
// This handler fires when a new database is created and indicates
// either that one has not been created before, or a new version
// was submitted with window.indexedDB.open(). (See above.)
// It is only implemented in recent browsers.
DBOpenRequest.onupgradeneeded = (event) => {
const db = event.target.result;
db.onerror = (event) => {
note.innerHTML += "<li>Error loading database.</li>";
};
// Create an objectStore for this database
const 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 });
objectStore.createIndex("notified", "notified", { unique: false });
};
Specifications
Specification |
---|
Indexed Database API 3.0 # ref-for-dom-idbobjectstore-createindex① |
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).