JavaScript returning the value from an inner function

Question

I am trying to get the value from an inner function. Why is domain always returning undefined? I think this is because the webSQL executes asynchronously. I need to get the value of domain at this point in the program before I can proceed. I think this is a closure problem but perhaps my approach is is just wrong?

var domain = selectDomain();

function selectDomain()
{
    var sql,
        i;

    sql = "SELECT * FROM Domain";

    database.open();
    database.query(sql, [], function(tx, result) 
    {
        for (i = 0; i < result.rows.length; i++)
        {
            var domain = result.rows.item(i);   
            return domain.Domain;
        }
    });
}

score 3 · Accepted Answer · answered Apr 12 '12 at 11:33

You're right that the query executes asynchronously, and a return statement here will not work. Instead, in the callback function of the query, call another function that passes the result as a parameter, and continue your program from there.

Edit: I just noticed that you loop through the result, which means domain will be continuously overwritten by each row, and always end up with the value of the last item.

var domain;
selectDomain();

function selectDomain() {
  ...

  database.query(sql, [], function(tx, result) 
  {
    for (i = 0; i < result.rows.length; i++)
    {
      handleResult(result.rows.item(i));
    }
  });
}

function handleResult(result) {
    domain = result.Domain;
    // Continue
}

JavaScript returning the value from an inner function

1 Answers1