Not able to understand how tag value is included from jsp page to js file

Question

I am facing a problem where I have button in jsp page if i click it then it opens the dialogue and for the first time I am opening it , it shows the title of the dialogue box but from the second time onwards it doesnt show the title of dialogue.. I just started working on javascript and jsp , here I need a little help to understand where this value is coming from ,

**if($('#add-meeting-time').size() == 0)
                    $('body').append('<div id="add-meeting-time" />');**

How #add-meeting-time tag value is coming from jsp and why it is fetching the tag value add-meeting-time from jsp first time and not from the second time. I have added the code below. please have a look and help thanks in advance.

function addMeetingTime(caseId, passedds) {
    showOverlay();
    $.ajax({        
        url :   'case/RepairPro_addInputAgreeMeetingEvent?passedds='+passedds,
        type :  'get',
        data :  'cid=' + caseId + "&t=" + Math.random(),
        success :    function(data) {
            if($('#add-meeting-time').size() == 0)
                $('body').append('<div id="add-meeting-time" />');
            $('#add-meeting-time').html(data);
            
            $( "#add-meeting-time" ).dialog({
                autoOpen: false,
                modal: true,
                width:650,
                buttons: {
                    action: {
                        text: getText('save'),
                        click: function() {
                            disableDialogButton();
                            $('#add-meeting-time form').submit();
                        }
                    },
                    cancel: {
                        text: getText('cancel'),
                        click: function() {
                            $( this ).dialog( "close" );
                        }
                    }
                },
                create: function() {
                    var datepickerSettings = {minDate: 0};
                    if (getConfig('isDisplayTimezone')) {
                        datepickerSettings = {}
                    }

                    if(getConfig('isCalendarModularEnabled')) {
                        if(localMember.myrole > parseInt(getGlobal('AUTH2'))) {
                            $(this).parent().find('.ui-dialog-title').before($("<a href='javascript:void(0);' onclick='addMeetingTimeCalendar(\"" + passedds + "\", " + caseId + ");' title=\"" + getText('calendar_view') + "\" style='float:left; margin-right:1em;' class='ui-icon extra-dialog-button'></a>")
                            .button({icons:{primary: "ui-icon-calendar"},text: false}));
                        }
                        else {
                            $(this).parent().find('.ui-dialog-title').before($("<a href='javascript:void(0);' onclick='addPersonalMeetingTimeCalendar(\"" + passedds + "\", " + caseId + ");' title=\"" + getText('calendar_view') + "\" style='float:left; margin-right:1em;' class='ui-icon extra-dialog-button'></a>")
                            .button({icons:{primary: "ui-icon-calendar"},text: false}));
                        }
                    }

                    $(this).find('.datepicker').datetimepicker(datepickerSettings);
                    showTaskError(this, 'refreshCaseMessagesPage()');
                    
                    initTeamMemberSelect();         
                },
                open: function() {
                    $('select[id=add-meeting-member] option:eq(1)').attr('selected', 'selected');
                    $('select[id=add-meeting-member] option:eq(0)').attr('selected', 'selected');
                },
                close: function() {
                    $( this ).dialog( "destroy" ).remove();
                }
            });
            $( '#add-meeting-time' ).dialog( 'open' );
        }



    });
}