JavaScript anonymous function variable

Question

I'm working on a PhoneGap app and I have this piece of code in a loop

htmlR += "html code here";
tx.executeSql('SELECT Question,Grp from KnowSelf where Dimension = "'+result.Dimension+'"', [], function(tx,resultR){

    var leng = resultR.rows.length;
    for(var i = 0; i < leng; i++){
        var resultsR = resultR.rows.item(i);
        htmlR += '<li class="catsli">'+resultsR.Question+'</li>';
        htmlR += '<li class="line"><img class="line" src="iPhone3/Line.png" alt="line"/></li>';

    }

},errorCB);
htmlR += "continue html code here";

My problem is, inside the tx.executeSql(.... htmlR += li tags

is not adding to the outer htmlR.

It should be, the function you're passing into executeSql is a closure over it and I don't see it being shadowed anywhere. Are you sure the callback accepted by executeSql happens synchronously? Sounds like it may be async, hence your not seeing the results immediately. — T.J. Crowder
– T.J. Crowder, Commented Dec 5, 2011 at 22:31
@T.J.Crowder: I strongly assume that it's async; otherwise, it wouldn't need a callback. — SLaks
– SLaks, Commented Dec 5, 2011 at 22:32
@SLaks: I expect so, but it's not the only reason for one. :-) — T.J. Crowder
– T.J. Crowder, Commented Dec 5, 2011 at 22:33

T.J. Crowder · Accepted Answer · 2011-12-05 22:34:32Z

3

I suspect that executeSQL doesn't call the callback immediately, but rather asynchronously, and so you don't see the results immediately. If so, the correct way to handle it is to do all of your processing that relies on the results from within the callback, rather than after calling executeSQL. E.g., change:

// Do Something
doSomething();

// Do some SQL
executeSQL(..., function() {
   // ...deal with callback...
});

// Do something after SQL
doSomethingElse();

to

// Do Something
doSomething();

// Do some SQL
executeSQL(..., function() {
   // ...deal with callback...

    // Do something after SQL
    doSomethingElse();
});

answered Dec 5, 2011 at 22:34

T.J. Crowder

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1 Comment

Mario Over a year ago

Although you're solution made sense, it does not work in my case. But thanks for the async tip, i will just change my logic

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