how to make scroll bar(even inactive) disappear using jquery

how to make scroll bar(even inactive) disappear using jquery

i want that when a div increase than a height i have set, then only it
should show scroll bar, otherwise the inactive scrollbar should also not
be shown.
i am using the following code for this:
$(document).ready(function(){
if($('.dialog-text').height()<=119 ){
$(this).css('overflow-y', "hidden");
}
else{
$(this).css('overflow-y', "scroll");
}
});
obviously i must have done something wrong. please point it out or give a
better solution.