how to set a variable inside of a callback function in JavaScript?

Question

i am testing Phonegap Web Storage for a small project:

var listsCount = 0;

tx.executeSql("SELECT * FROM list WHERE id = ?", [id], successGetList, errorGetList );

function successGetList(tx, results){
    listsCount = results.rows.length; // this will be 2, in my case
}

function errorGetList(err){
    console.log("Error processing SQL: "+err.code);
}

console.log(listsCount); // this will show 0, instead of 2

the issue i'm having is that listsCount doesn't get set inside the successGetList method. Even if i return it there.

any ideas on how can i set that variable inside of successGetList function ?

thanks

Possible duplicate of [How to return the response from an AJAX call from a function?](http://stackoverflow.com/questions/14220321/how-to-return-the-response-from-an-ajax-call-from-a-function) (Granted, this not AJAX, but the same asynchronous behavior applies.) — Frédéric Hamidi, Feb 18 '13 at 18:54
@FrédéricHamidi This is not asking about `return` either. You're right that the answer there should point the right direction, but maybe that's too much for this particular question. — bfavaretto, Feb 18 '13 at 19:00

score 4 · Accepted Answer · answered Feb 18 '13 at 18:53

4

It does get set, but your console.log call is being fired before that (that's how asynchronous code works!). Just use the value from the callback. If you need, call another function from there, and pass your data to it.

answered Feb 18 '13 at 18:53

bfavaretto

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`Just use the value from the callback`, how? – Patrioticcow Feb 18 '13 at 19:15
I mean use `results.rows.length` from inside `successGetList`, or call another function from there and pass it. The exact answer will depend on what you want to do with the value... – bfavaretto Feb 18 '13 at 19:15
got it. didn't notice that the callback is asynchronous. thanks – Patrioticcow Feb 18 '13 at 19:17

how to set a variable inside of a callback function in JavaScript?

1 Answers1