CRUD using indexedDB/WebSQL sample code

This sample code is part of an app I am working at. I am kind of newbie, so please give some constructive feedback. The code is based on this sample code: http://nparashuram.com/trialtool/#example=/IndexedDB/trialtool/index.html&selected=

For WebSQL compatibility use his IndexedDBShim (http://nparashuram.com/IndexedDBShim/)

I think it is much easier to pick this code and adapt it for your own scenario. You are welcome to come with improvements.

If this is difficult to read get the script from this link:
https://www.dropbox.com/s/kc5rjp8dmwcl1ze/myIndexedDB.js

/* -------------------------- */
/* myindexedDB
/* -------------------------- */

var indexedDBModule = (function(){

//'global' index; 
var i = 0;
//keep a refference to the database name in dbName
var dbName;

//prefixes of implementation that we want to Test
var indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB;
//not used yet
var IDBTransaction = window.IDBTransaction || window.webkitIDBTransaction || window.msIDBTransaction;
var IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange || window.msIDBKeyRange;

var init = function(db,store) {
    if (!indexedDB) {
        alert("Sorry!Your browser doesn't support IndexedDB");
    } else {
        initDB(db,store);
    }
}; 

var destroy = function(db){
    try {
        //request to delete the entire database
        if(!db || db=='')
            var dbDeleteRequest = indexedDB.deleteDatabase(DB_NAME);
        else var dbDeleteRequest = indexedDB.deleteDatabase(db);
        dbDeleteRequest.onsuccess = function(e) {
            alert('Database successfully deleted');
            /*
             * I found out that when I need to destroy the database and recreate 
             * it, there are some issues. I tried to destroy database, create database,
             * insert items, deleteAllItems, count the items in the objectStore etc...  
             * after destroying the database, a location.reaload() helps refreshing these operations
             */
            location.reload();               
        };
        dbDeleteRequest.onupgradeneeded = function(e) {
            console.log('Database upgrade needed ');
        };
        dbDeleteRequest.onerror = function(e) {
            console.log('Error deleting database ');
        };
        dbDeleteRequest.onblocked = function(e) {
            console.log('Deleting Database Blocked... Try closing the database and then deleting it ');
        };
    } catch (e) {
        console.log(e);
        alert('Error on destroy -> deleteDatabase ');
    }
};

var createItem = function(id,data,store,update){    
    try {
        //request to open the database
        var dbOpenRequest = indexedDB.open(dbName);
        dbOpenRequest.onsuccess = function(event) {
            var thisDB = dbOpenRequest.result;
            thisDB.onversionchange = function(e) {
                console.log('Version change triggered, so closing database connection ' + e.oldVersion + ' ' + e.newVersion + ' ' +thisDB);
                thisDB.close();
            };
            try{
                var transaction = thisDB.transaction([store], "readwrite");
                transaction.oncomplete = function(e) {
                    console.log('transaction is complete ');
                };
                transaction.onabort = function(e) {
                    var error = e.target.error; // DOMError
                    if (error.name == 'QuotaExceededError') {
                        alert('createItem -> transaction['+store+'] -> onabort - QuotaExceededError ');
                    }
                    console.log('transaction aborted ');
                };
                transaction.onerror = function(e) {
                    console.log('transaction error');
                };
                try {
                    var request;
                    var objectStore = transaction.objectStore(store);
                    if(update && update==true){
                        //request to UPDATE new entry in the object store
                        request = objectStore.put(data);
                    } else{
                        //request to ADD entry in the object store
                        request = objectStore.add(data);    
                    }                     
                    request.onsuccess = function(event) {
                        //var element = event.target.result;
                        if(update && update == true)
                            console.log('The record with ID = ' + id + ' has been updated in the database ');
                        else console.log('A new record with ID = ' + id + ' has been added to the database ');                            
                    };
                    request.onerror = function(event) {
                        if (update && update == true){
                            console.log('Error. Could not update record with id = ' + id);
                        }
                        else {
                            console.log('Error ' + event + ' This record is already in the database. ');
                        }
                    }; 
                } catch (e) {
                    console.log('Could not operate on '+ '['+store+']' +'. You may have to create it first ');
                };
            } catch(e){
                console.log('Error ' + e);
            };
        };
        dbOpenRequest.onupgradeneeded = function(e) {
            console.log('Database upgrade needed ');
            //not used
            //var db = dbOpenRequest.result;
            //var transaction = dbOpenRequest.transaction;
        };
        dbOpenRequest.onerror = function(e){
            console.log('Error ');
        };
        dbOpenRequest.onblocked = function(e) {
            console.log('Database open request blocked ');
        };
    } catch(e){
        console.log('Error ');
    };
};

var readItem = function(id,store) {
    try {
        var dbOpenRequest = indexedDB.open(dbName);
        dbOpenRequest.onsuccess = function(event) {
            var thisDB = dbOpenRequest.result;
            thisDB.onversionchange = function(e) {
                console.log('Version change triggered, so closing database connection ' + e.oldVersion + ' ' + e.newVersion + ' ' +thisDB);
                thisDB.close();
            };
            try{
                var transaction = thisDB.transaction([store], "readonly");
                transaction.oncomplete = function(e) {
                    console.log('transaction is complete ');
                };
                transaction.onabort = function(e) {
                    console.log('transaction aborted ');
                };
                transaction.onerror = function(e) {
                    console.log('transaction error ');
                };

                try {
                    var objectStore = transaction.objectStore(store);
                    var request = objectStore.get(id);
                    request.onsuccess = function(event) {
                        var element = event.target.result;
                        if(element!==undefined){
                            console.log('Elemtent with id = ' + id + ' was found\n' + JSON.stringify(element));
                        }
                        else{
                            console.log('Element with id = ' + id + ' does not exist in the IndexedDB ');
                        }
                    };
                    request.onerror = function(event){
                        console.log('Error - could not request data from the object store ' + event);
                    };
                } catch (e) {
                    console.log('Could not operate on '+ '['+store+']' +'. You may have to create it first ');
                }
            } catch(e){
                console.log('Error ');
            }
        };
        dbOpenRequest.onupgradeneeded = function(e) {
            console.log('Database upgrade needed ');
            //var db = dbOpenRequest.result;
            //var transaction = dbOpenRequest.transaction;
        };
        dbOpenRequest.onerror = function(e){
            console.log('Error ');
        };
        dbOpenRequest.onblocked = function(e) {
            console.log('Database open request is blocked ');
        };
    } catch(e){
        console.log('Error ');
    };
};

var updateItem = function(id,data,store){
    createItem(id,data,store,true);
};

var deleteItem = function(id,store) {
    try {
        var dbOpenRequest = indexedDB.open(dbName);
        dbOpenRequest.onsuccess = function(event) {
            var thisDB = dbOpenRequest.result;
            thisDB.onversionchange = function(e) {
                console.log('Version change triggered, so closing database connection ' + e.oldVersion + ' ' + e.newVersion + ' ' +thisDB);
                thisDB.close();
            };
            try{
                //attempt to create a transaction
                var transaction = thisDB.transaction([store], "readwrite");
                transaction.oncomplete = function(e) {
                    console.log('transaction is complete ');
                };
                transaction.onabort = function(e) {
                    console.log('transaction aborted ');
                };
                transaction.onerror = function(e) {
                    console.log('Transaction error -> [deleteItem] ');
                };

                try {
                    var objectStore = transaction.objectStore(store);
                    var getRequest = objectStore.get(id);
                    getRequest.onsuccess = function(e){
                        if (e.target.result != null) {
                            console.log('Object Exist');
                            //request to delete entry from the object store                        
                            var request = objectStore.delete(id);
                            request.onsuccess = function(event){
                                console.log('Entry id = ' + id + ' was deleted from the database');
                            };
                            request.onerror = function(event){
                                console.log('Error [deleteItem] -> delete('+id+') ');
                            };        
                        }else{
                            console.log('Object doesn\'t exist ');
                        }
                    };
                    getRequest.onerror = function(e){
                        console.log('Error [deleteItem] -> delete('+id+') ');
                    };
                } catch (e) {
                    console.log('Could not operate on '+ '['+store+']' +'. You may have to create the entry first ');
                }
            } catch(e){
                console.log('Error ');
            }
        };
        dbOpenRequest.onupgradeneeded = function(e) {
            console.log('Database upgrade needed ');
            //var db = dbOpenRequest.result;
            //var transaction = dbOpenRequest.transaction;
        };
        dbOpenRequest.onerror = function(e){
            console.log('Error ');
        };
        dbOpenRequest.onblocked = function(e) {
            console.log('Database open request is blocked ');
        };
    } catch(e){
        console.log('Error ');
    }
};

var insertItems = function(store,obj,length){
    //inserts the same item multiple times in the same transaction.
    //just a test
    try {
        //request to open the database
        var dbOpenRequest = indexedDB.open(dbName);
        dbOpenRequest.onsuccess = function(event) {
            var thisDB = dbOpenRequest.result;
            thisDB.onversionchange = function(e) {
                console.log('Version change triggered, so closing database connection ' + e.oldVersion + ' ' + e.newVersion + ' ' +thisDB);
                thisDB.close();
            };
            try{
                //creating transaction to open an object store in "readwrite" mode
                var transaction = thisDB.transaction([store], 'readwrite');
                transaction.oncomplete = function(e) {
                    console.log('transaction is complete ');
                };
                transaction.onabort = function(e) {
                    var error = e.target.error; // DOMError
                    console.log('transaction aborted ' + error);
                };
                transaction.onerror = function(e) {
                    console.log('transaction error ');
                };

                try {
                    var request;
                    var objectStore = transaction.objectStore(store);

                    putNext();

                    function putNext() {
                        if (i<length) {
                            objectStore.add(JSON.parse(obj)).onsuccess = putNext;
                            //console.log('add entry with id = ' + i);
                            ++i;
                        } else {   
                            // complete
                            console.log('insertItems -> DONE');
                            //callback();
                        }
                    }
                } catch (e) {
                    console.log('Could not operate on '+ '['+store+']' +'. You may have to create it first ');
                };
            } catch(e){
                console.log('Error ');
            };
            //when done 
            //callback();
        };
        dbOpenRequest.onupgradeneeded = function(e) {
            console.log('Database upgrade needed ');
        };
        dbOpenRequest.onerror = function(e){
            console.log('Error ');
        };
        dbOpenRequest.onblocked = function(e) {
            console.log('Database open request blocked ');
        };
    } catch(e){
        console.log('Error ');
    };
};

var readAllItems = function(store) {
    try {
        var dbOpenRequest = indexedDB.open(dbName);
        dbOpenRequest.onsuccess = function(event) {
            var thisDB = dbOpenRequest.result;
            thisDB.onversionchange = function(e) {
                console.log('Version change triggered, so closing database connection ' + e.oldVersion + ' ' + e.newVersion + ' ' +thisDB);
                thisDB.close();
            };
            try{
                var transaction = thisDB.transaction([store], "readonly");
                transaction.oncomplete = function(e) {
                    console.log('transaction is complete ');
                };
                transaction.onabort = function(e) {
                    console.log('transaction aborted ');
                };
                transaction.onerror = function(e) {
                    console.log('transaction error ');
                };
                try {
                    var objectStore = transaction.objectStore(store);                        
                    //request cursor on the object store
                    var request = objectStore.openCursor();
                    var count = 0;
                    request.onsuccess = function(event) {
                        var cursor = event.target.result;
                        if (cursor) {                              
                            console.log('id = ' + cursor.key + ' is ' + cursor.value);
                            count++;
                            cursor['continue']();
                        } else console.log('Total entries = ' + count);
                    };
                    request.onerror = function(e){
                        console.log('transaction error on readAllItems -> oenCursor -> onerror ');
                    };
                } catch (e) {
                    console.log('Could not operate on '+ '['+store+']' +'. You may have to create it first ');
                }
            } catch(e){
                console.log('Error ');
            }
        };
        dbOpenRequest.onupgradeneeded = function(e) {
            console.log('Database upgrade needed ');
            //var db = dbOpenRequest.result;
            //var transaction = dbOpenRequest.transaction;
        };
        dbOpenRequest.onerror = function(e){
            console.log('Error ');
        };
        dbOpenRequest.onblocked = function(e) {
            console.log('Database open request is blocked ');
        };
    } catch(e){
        console.log('Error ');
    }
};

var deleteAllItems = function(store,count){
    try {
        var dbOpenRequest = indexedDB.open(dbName);
        dbOpenRequest.onsuccess = function(event) {
            var thisDB = dbOpenRequest.result;
            thisDB.onversionchange = function(e) {
                console.log('Version change triggered, so closing database connection ' + e.oldVersion + ' ' + e.newVersion + ' ' +thisDB);
                thisDB.close();
            };
            try{
                var transaction = thisDB.transaction([store], "readwrite");
                transaction.oncomplete = function(e) {
                    console.log('transaction is complete ');
                };
                transaction.onabort = function(e) {
                    console.log('transaction aborted ');
                };
                transaction.onerror = function(e) {
                    console.log('transaction error ');
                };
                try {
                    //open object store
                    var objectStore = transaction.objectStore(store);
                    try{
                        //count items in the object store
                        var requestCount = objectStore.count();
                        requestCount.onsuccess = function(event){
                            if(requestCount.result){
                                console.log('There are '+requestCount.result+' entries in the database.');
                            }
                            else{
                                if(requestCount.result!=0){
                                    //request to clear the object store                        
                                    var request = objectStore.clear();
                                    request.onsuccess = function(event) {
                                        console.log('No more entries to delete in the object store!');
                                        //reset 'global' index
                                        i = 0;                            
                                    };
                                    request.onerror = function(event) {
                                        console.log('Error clearing the object store! ' + event);
                                    };
                                }
                                else {
                                    console.log('Object store is already empty');
                                }    
                            }
                        };
                        requestCount.onerror = function(event){
                            console.log('Error counting elements in the store ');
                        };
                    } catch(e){
                        console.log('Error ');
                    }                      
                } catch (e) {
                    console.log('Could not operate on '+ '['+store+']' +'. You may have to create it first ');
                }
            } catch(e){
                console.log('Error ');
            }
        };
        dbOpenRequest.onupgradeneeded = function(e) {
            console.log('Database upgrade needed ');
        };
        dbOpenRequest.onerror = function(e){
            console.log('Error ');
        };
        dbOpenRequest.onblocked = function(e) {
            console.log('Database open request is blocked ');
        };
    } catch(e){
        console.log('Error ');
    }
};

/************ helper functions ****************/    
function initDB(db,store) {
    try {
        var dbOpenRequest = indexedDB.open(db,1);
        dbOpenRequest.onsuccess = function(event) {
            var thisDB = dbOpenRequest.result;
            // Need to create this variable since the variable db is assigned to other things later
            thisDB.onversionchange = function(e) {
                console.log('Version change triggered, so closing database connection ' + e.oldVersion + ' ' + e.newVersion + ' ' + thisDB);
                thisDB.close();
            };
            console.log('Database '+db+' is created with objectStore '+store);
            dbName = db;
        };
        dbOpenRequest.onupgradeneeded = function(e) {
            var thisDB = dbOpenRequest.result;
            var transaction = dbOpenRequest.transaction;
            try {
                var storeOptions = {autoIncrement : true}; //possible pass storeOptions in init and further to initDB
                var objectStore = thisDB.createObjectStore(store,storeOptions);

            } catch (e) {
                console.log('Error occured while creating object store ');
            }                
        };
        dbOpenRequest.onerror = function(e) {
            console.log('Error ');
        };
        dbOpenRequest.onblocked = function(e) {
            console.log('Blocked ');
        };
    } catch (e){
        console.log('Error ');
    }
}
/******** helpers **********/

return{
    init : init, 
    destroy : destroy,
    createItem : createItem,
    readItem : readItem,
    updateItem : updateItem,
    deleteItem : deleteItem,
    insertItems : insertItems,
    readAllItems : readAllItems,         
    deleteAllItems : deleteAllItems
};
}());