Web/API/IDBObjectStore/createIndex

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

var myIDBIndex = objectStore.createIndex(indexName, keyPath);
var myIDBIndex = objectStore.createIndex(indexName, keyPath, objectParameters);

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 a keyPath.

objectParameters Optional

An IDBIndexParameters object, which can include the following properties:

Attribute Description

unique If true, the index will not allow duplicate values for a single key.

multiEntry If true, the index will add an entry in the index for each array element when the keyPath resolves to an Array. If false, it will add one single entry containing the Array.

locale

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, or pl.
auto: The platform default locale will be used (may be changed by user agent settings.)
null or undefined: 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:

Exception	Description
`ConstraintError`	Occurs if an index with the same name already exists in the database. Index names are case-sensitive.
`InvalidAccessError`	Occurs if the provided key path is a sequence, and `multiEntry` is set to `true` in the `objectParameters` object.
`InvalidStateError`	Occurs if either: The method was not called from a `versionchange` transaction mode callback, i.e. from inside a `IDBOpenDBRequest.onupgradeneeded` handler. The object store has been deleted.
`SyntaxError`	Occurs if the provided `keyPath` is not a valid key path.
`TransactionInactiveError`	Occurs if the transaction this `IDBObjectStore` belongs to is not active (e.g. has been deleted or removed.) In Firefox previous to version 41, an `InvalidStateError` was raised in this case as well, which was misleading; this has now been fixed (see bug 1176165.)

Example

In the following example you can see the IDBOpenDBRequest.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 ([[../../../../../../../mdn.github.io/to-do-notifications/index|view example live]].)

var db;

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

// Two event handlers for opening the database.
DBOpenRequest.onerror = function(event) {
  note.innerHTML += '<li>Error loading database.</li>';
};

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 = 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 = function(event) {
  var db = event.target.result;
 
  db.onerror = function(event) {
    note.innerHTML += '<li>Error loading database.</li>';
  };

  // 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 });
  objectStore.createIndex("notified", "notified", { unique: false });
};

Specifications

Specification	Status	Comment
Indexed Database API 2.0The definition of 'createIndex()' in that specification.	Recommendation
Indexed Database API DraftThe definition of 'createIndex()' in that specification.	Recommendation

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`createIndex`	Chrome Full support 24 Full support 24 No support 23 — 57 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Edge Full support 12	Firefox Full support 16 Full support 16 No support 10 — 16 Prefixed' Prefixed' Implemented with the vendor prefix: moz	IE Partial support 10	Opera Full support 15	Safari Full support 7	WebView Android Full support Yes Full support Yes No support ? — 57 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Chrome Android Full support 25 Full support 25 No support 25 — 57 Prefixed' Prefixed' Implemented with the vendor prefix: webkit	Firefox Android Full support 22	Opera Android Full support 14	Safari iOS Full support 8	Samsung Internet Android Full support 1.5 Full support 1.5 No support 1.5 — 7.0 Prefixed' Prefixed' Implemented with the vendor prefix: webkit

Legend

Full support: Full support
Partial support: Partial support
Requires a vendor prefix or different name for use.': Requires a vendor prefix or different name for use.