IDBObjectStore: createIndex() method

BaselineWidely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

Note: This feature is available inWeb Workers.

ThecreateIndex() method of theIDBObjectStore interface creates and returns a newIDBIndex object in the connected database. It creates a newfield/column defining a new data point for each database record to contain.

Bear in mind that IndexedDB indexes can containany JavaScript data type;IndexedDB uses thestructured clone algorithm to serialize stored objects, which allows for storage of simpleand complex objects.

Note that this method must be called only from aVersionChange transactionmode callback.

Syntax

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 emptykeyPath, and also to pass in a sequence (array) as akeyPath.

optionsOptional

An object which can include the followingproperties:

unique

Iftrue, the index will not allow duplicate values for a single key. Defaults tofalse.

multiEntry

Iftrue, 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.

localeNon-standard Deprecated

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.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

AnIDBIndex object: the newly created index.

Exceptions

This method may raise aDOMException of one of the following types:

ConstraintErrorDOMException

Thrown if an index with the same name already exists in the database. Index names are case-sensitive.

InvalidAccessErrorDOMException

Thrown if the provided key path is a sequence, andmultiEntry is set totrue in theobjectParameters object.

InvalidStateErrorDOMException

Thrown if:

The method was not called from aversionchange transaction mode callback, i.e., from inside aonupgradeneeded handler.
The object store has been deleted.

SyntaxErrorDOMException

Thrown if the providedkeyPath is not avalid key path.

TransactionInactiveErrorDOMException

Thrown if the transaction thisIDBObjectStorebelongs to is not active (e.g., has been deleted or removed.) In Firefoxprevious to version 41, anInvalidStateError was raised inthis case as well, which was misleading; this has now been fixed (seeFirefox bug 1176165.)

Examples

In the following example you can seetheonupgradeneeded handler being used to update thedatabase structure if a database with a higher version number is loaded.createIndex() is used to create new indexes on the object store. For afull working example, see ourTo-do Notifications app (view example live).

let db;// Let us open our databaseconst DBOpenRequest = window.indexedDB.open("toDoList", 4);// Two event handlers for opening the database.DBOpenRequest.onerror = (event) => {  note.appendChild(document.createElement("li")).textContent =    "Error loading database.";};DBOpenRequest.onsuccess = (event) => {  note.appendChild(document.createElement("li")).textContent =    "Database initialized.";  // 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.appendChild(document.createElement("li")).textContent =      "Error loading database.";  };  // 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 });};