SQlite database with PhoneGap and JavaScript

Question

I'm using PhoneGap and a SQLite Database.

I try something like this:

I have a function useSavedThing():

function useSavedThing() {

        alert("BEFORE getSavedThing()");    

    getSavedThing();

        alert("AFTER getSavedThing()");

}

and a function getSavedThing():

function getSavedThing(){

        alert("ONE");
        var db = window.openDatabase("Database", "1.0", "Database", 200000);
    db.transaction(populateDB, errorCB, successCB);
        alert("TWO");
    function populateDB(tx) {

        alert("THREE");
    }

    function errorCB(tx, err) {
        alert("Error processing SQL: " + err);
    }

    function successCB() {
        alert("FOUR");
        db.transaction(getData);
    }

    function getData(tx) {
                alert("FIVE");
        tx.executeSql('SELECT * FROM SETTINGS', [], getIt, errorCB);
    }
    function getIt(tx, results) {
                   alert("SIX");
            var savedthing = results.rows.item(0).data;


    }



}

The problem is that when the function getSavedThing() is called, only the first two alerts (alert("ONE"), alert("TWO)) issued but then the alert ("AFTER getSavedThing ()") called.

But I want that all expenses alert ("ONE"), alert ("TWO"), alert ("THREE") alert ("FOUR") alert ("FIVE"), alert ("SIX"), issued before the alert("AFTER getSavedThing()"); appers.

The order fo the alerts should be:

1. alert("BEFORE getSavedThing()");
2. alert("ONE");
3. alert("TWO");
4. alert("THREE");
5. alert("FOUR");
6. alert("FIVE");
7. alert("SIX");
8. alert("BEFORE getSavedThing()");

Can someone help me?

Answer 1

Database operations are performed asynchronously. If you want alert("AFTER getSavedThing()") to be executed after the last database operation it needs to be called from the callback function getIt() ;

function useSavedThing() {
    alert("BEFORE getSavedThing()");
    var afterGet = function(){
        alert("AFTER getSavedThing()");
    }
    getSavedThing( afterGet ); /*pass the callback function to getSavedThing*/
}

function getSavedThing( callback ){

    alert("ONE");
    var db = window.openDatabase("Database", "1.0", "Database", 200000);
    db.transaction(populateDB, errorCB, successCB);
    alert("TWO");
    function populateDB(tx) {
        alert("THREE");
    }

    function errorCB(tx, err) {
        alert("Error processing SQL: " + err);
    }

    function successCB() {
        alert("FOUR");
        db.transaction(getData);
    }

    function getData(tx) {
        alert("FIVE");
        tx.executeSql('SELECT * FROM SETTINGS', [], getIt, errorCB);
    }

    function getIt(tx, results) {
         alert("SIX");
         var savedthing = results.rows.item(0).data;
         callback.call(); /*execute the callback function*/
    }
}

Answer 2

You can use this framework for data access in PhoneGap, you will find it quite easy to use:

var db = new MyDB();
//query all users
var users = db.Users.toArrary(callback);