returning results from functions - javascript

Question

I defined the following Javascript function:

function RecoverDataFromTable(table_name) {
              query = "";

              //some code that build a query string from table_name and
              //other arguments given to the function

              function Query(database) {
              database.executeSql(query, [], RecoverResults, Error)
              }

              function RecoverResults(database, results) {
              var my_result = results.rows(0).id;
              // assume this works and store a value to my_result
              }

              function Error(error) {
              //alert something
              }

              function Success() {
              //alert something
              }

              database.transaction(Query, Error, Success)                 

              }

Now, how can i return my_result value so i can do this?

var my_var = RecoverDataFromTable(table_name, argument1, argument2.....)

Thanks in advance. Ask if you need more explanation. :)

http://www.raymondcamden.com/index.cfm/2012/1/6/Working-with-dates-and-SQLite-in-PhoneGap

**Error** and **Success** are callbacks... are they asynchronous? — McGarnagle, Apr 24 '12 at 07:24
Ok ... can you provide any more info on what **database** is? Seems like it's a JS library. — McGarnagle, Apr 24 '12 at 07:50
that's a web sql database using sql lite. I'm writing a phonegap app on iOs. — Stefano, Apr 24 '12 at 07:56
possible duplicate of [How to return the response from an AJAX call?](http://stackoverflow.com/questions/14220321/how-to-return-the-response-from-an-ajax-call) — Farid Nouri Neshat, May 03 '14 at 06:31
possible duplicate of [How to return value from an asynchronous callback function?](http://stackoverflow.com/questions/6847697/how-to-return-value-from-an-asynchronous-callback-function) — Qantas 94 Heavy, May 03 '14 at 10:13

score 1 · Accepted Answer · answered Apr 24 '12 at 08:06

You can't really set the variable like that, because the function is asynchronous. Instead, you should include a callback function in your request to RecoverDataFromTable. Define it like this:

function RecoverDataFromTable(callback, table_name) {
     ...

     function RecoverResults(database, results) {
          var my_result = results.rows(0).id;
          // assume this works and store a value to my_result
          // make the callback:
          callback(result);
     }
     ...
}

Then make the call like this:

function handleResult(my_result)
{
    // handle the result here
}

RecoverDataFromTable(handleResult, table_name, argument1, argument2.....);

score 0 · Answer 2 · answered Apr 24 '12 at 07:52

0

If your function RecoverResults is asynchronous, then you can use to::

function RecoverDataFromTable(callback, table_name) {
      ...
      function RecoverResults(callback, database, results) {
          var my_result = results.rows(0).id;
          callback(my_result);
          // assume this works and store a value to my_result
      }
}
RecoverDataFromTable(function(result) {
    var my_var = result;

}, table_name, argument1, argument2.....);

answered Apr 24 '12 at 07:52

belykh

1,109
10
25

this is very similar to the correct answer. It doesn't work because there's callback in RecoverResults arguments. Thanks anyway :) – Stefano Apr 24 '12 at 08:35

score 0 · Answer 3 · answered Apr 24 '12 at 07:56

0

isn't it just?

function RecoverResults(database, results) {
 return results.rows(0).id;
}

var my_result = RecoverResults();

answered Apr 24 '12 at 07:56

Burntime

2,334
2
15
20

No, because it looks like the function is asynchronous ... – McGarnagle Apr 24 '12 at 07:59

returning results from functions - javascript

3 Answers3