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    IDBObjectStore.createIndex()

    This article is in need of a technical review.

    The createIndex() method of the IDBObjectStore interface creates and returns a new IDBIndex object in the connected database.

    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.

    Exceptions

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

    Exception Description
    InvalidStateError The IDBObjectStore has been deleted or removed or the method was not called from a versionchange transaction mode callback.
    ConstraintError 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 });
    };

    Parameters

    indexName
    The name of the index to create.
    keyPath
    The key path for the index to use.
    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.

    Specifications

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

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
    Basic support 23webkit
    24
    10 moz
    16.0 (16.0)
    10, partial 15 7.1
    Feature Android Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
    Basic support 4.4 22.0 (22.0) 1.0.1 10 22 Not supported

    See also

     

     

    Document Tags and Contributors

    Contributors to this page: mattandrews, fscholz, chrisdavidmills
    Last updated by: fscholz,