function(instanceData, cid)

Creates a new record given the serialized form of the data. Resolves to a promise with any additional properties that should be added to the instance. A client ID is passed of the instance that is being created.

The following shows how constructor calls createData and what it does with the response:

import CID from "can-util/js/cid/cid";

// Create an instance of a special type
const myInstance = new MyType( { /* ... */ } );

// get its CID
const cid = CID( myInstance );

// get its raw data
const instanceData = connection.serializeInstance( myInstance );

connection.createData( instanceData, cid ).then( function( createdInstanceData ) {
    connection.createdInstance( myInstance, createdInstanceData );
} );