ServiceNow GlideDialogWindow to open popup with cancel, discard , confirm button ServiceNow

ServiceNow GlideDialogWindow to pass data from client script to ui page

Client Script code

function onChange(control, oldValue, newValue, isLoading) {
    if (isLoading || newValue == '') {
          return;
    }
 var gdw = new GlideDialogWindow('ui_page_name');
      gdw.setTitle('Confirmation');
     gdw.setPreference('sysparm_oldValue', 'oldValue');
      gdw.render();
}

UI Page : ui_page_name

HTML

<?xml version="1.0" encoding="utf-8" ?>
<j:jelly trim="false" xmlns:j="jelly:core" xmlns:g="glide" xmlns:j2="null" xmlns:g2="null">
    <j:set var="jvar_renew_contact" value="${RP.getWindowProperties().get('sysparm_oldValue')}" />
<div>
     ${jvar_renew_contact}
 <p>Warning: Changes to Start dates or End dates for a Demand or Project will reset ALL active Resource Plans to a \"Requested\" state, will reset the Resource Plan dates and will require Resource Managers to reapprove all of the associated Resource Plans.</p>
 <button type="button"  onclick="cancelpop1()">Confirm</button>
  <button type="button" onclick="cancelpop('${jvar_renew_contact}')">Cancel</button>
  <button type="button"  onclick="cancelpop( '${jvar_renew_contact}')">Discard</button>
  </div></j:jelly>

Client Controller:

function cancelpop(val) {
    var gdw = GlideDialogWindow.get();
  g_form.setValue("start_date",val);
    gdw.destroy();
}
 function cancelpop1() {
    var gdw = GlideDialogWindow.get();
     gdw.destroy();
}