IDBObjectStore.createIndex

Note that this method must be called only from a VersionChange transaction mode callback.

Syntax

objectStore.createIndex(objectIndexName, objectKeypath, optionalObjectParameters);

Returns

An IDBIndex object: the newly created index.

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 an array as a keyPath.

optionalParameters

The IDBIndexParameters object — whose attributes are optional parameters to the method — 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.

Exceptions

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

Exception	Description
InvalidStateError	Occurs if the method was not called from a versionchange transaction mode callback.
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.)
ConstraintError	Occurs if an index with the same name (case-sensitive) already exists in the database.

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 (view example live.)

var db;

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

// these two event handlers act on the database being opened successfully, or not
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 event handles the event whereby a new version of the database needs to be created
// Either one has not been created before, or a new version number has been submitted via the
// window.indexedDB.open line 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 The definition of 'createIndex()' in that specification.	Recommendation

Browser compatibility

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.)