Client Catalog script getRowCount() not working

[servicetrout]

I have a catalog client script below on a catalog item, Type = onChange, Variable name = rpType, applies to Catalog Item view (checked). 

In the Background, this code:

var n = getNextTbn();
gs.print('Final TBN: ' + n);

function getNextTbn() {
var tbnCount=0; 
var gr = new GlideRecord('u_badgtbn');
gr.query();
gs.print("Nn: " + gr.getRowCount() );
tbnCount = pad(gr.getRowCount(), 9);
return tbnCount;
}

function pad(num, size) {
var s = "000000000" + num;
return s.substr(s.length-size);
}

Returns this: 

Script execution history and recovery

---

*** Script: Nn: 1
*** Script: Final TBN: 000000001

In my client script below, just shows the alerts

Precall...

1...

Then nothing. 

function onChange(control, oldValue, newValue, isLoading) {
if (isLoading || newValue == '') {
return;
}

var rpIdentifier = g_form.getValue('rpIdentifier');
if ( rpIdentifier.length < 2 ) {
alert ('Precall...');
var nNext = getNextTbn(); 
alert ("nNext: " + nNext);
g_form.setValue('rpIdentifier', nNext );
alert ('postCall... ' , nNext );
}
}

function getNextTbn() {
var tbnCount=0; 
var gr = new GlideRecord('u_badgtbn');
gr.query();
alert ("1...");
alert("Nn: " + gr.getRowCount() );
alert ("2...");
tbnCount = pad(gr.getRowCount(), 9);
alert ("3...");
return tbnCount;
}

function pad(num, size) {
var s = "000000000" + num;
return s.substr(s.length-size);
}

 Any idea why that would be the case?  Table u_badgtbn has read and write ACLs set to public.  Nothing showing up in any of the logs on this.

[SanjivMeher · Accepted solution]

Lot of GlideRecord function wont work in Client Script. That's why you need to use Glideajax for such use cases.

[servicetrout]

Ah!  Good to know.  Thank you. 

[benlittle]

From client side, you can't use getRowCount(). However, gr.rows.length will return what you are looking for without a GlideAjax call.

[benlittle]

Ironically, if you use the callback function, getRowCount() does work.

gCI.query(myCallbackFunction);

    function myCallbackFunction(gCI) {
          gCI.getRowCount();    //Does return the correct value
    }