Question

I’m creating a Phonegap application that will perform differently on first run. The way that I am detecting the first run is by seeing of one of the database tables exists. As you can probably tell from the code below, I am checking for the error that is (probably) indicating that the table already exists, thus proving that this is not the application’s first run.

function databaseExists(){
var exists;
database.transaction(function(tx){
    tx.executeSql('CREATE TABLE GLOBAL (uid, property, value)');
}, function(err){
    exists = true;
}, function(){
    exists = false;
});
return exists;
}

My problem, however, is that the asynchronous execution of the Javascript code means that the function returns its value before the success (or error) function has set it’s value.

This function is called in the initialising stage of the application:

if (databaseExists()){
    // Do Something
}

And therefore must return the value rather than execute the function in the success callback of the transaction.

Is there a way to force the execution to wait until the database transaction is complete or return the value through the database.transaction object?

Thanks in advance,
Jon

Answer 1

You need to write it in callback form:

var dataBaseExists(yep, nope) {
  database.transaction(function(tx) {
    tx.executeSql('CREATE TABLE GLOBAL (uid, property, value)');
  }, function(){
    if (yep) {
      yep.apply(this, arguments);
    }
  }, function(){
    if (nope) {
      nope.apply(this, arguments);
    }
  });
};


var itDoes = function() {
  console.log("great");
};

var itDoesNot = function() {
  console.log("what a pity");
};


databaseExists(itDoes, itDoesNot);