Why is my google apps script passing a value in one function and a NaN in the other? -

i'm using doget() example code passing values hidden object. works in first case of adding column on delcolumn nan/undefined in logger. trying figure out why code looks identical google tutorial.

function onopen() {      var ss = spreadsheetapp.getactivespreadsheet();    var menuentries = [ {name: "buildui", functionname: "buildui"} ];   ss.addmenu("buildui", menuentries);  }   function buildui()    {     var appheight =360   var app = uiapp.createapplication().setwidth(500).setheight(appheight).settitle('step 1:  pickboxes');   var ss = spreadsheetapp.getactivespreadsheet();   var panel = app.createverticalpanel().setid("settingspanel");    var headerpanel = app.createverticalpanel().setid("headerpanel").setstyleattribute("background", "silver").setwidth(500);   var columnpanel = app.createverticalpanel();   var maingrid = app.creategrid(5, 1).setid("maingrid");   var scroller =app.createscrollpanel();   var hidinstallcolumns =app.createtextbox().setid("hidinstallcolumns").setname("hidinstallcolumns").setvalue("1");    var columngrid =app.creategrid(1,1).setid("columngrid");   var headerlabel = app.createlabel("headerlabel").setstyleattribute("background", "silver").setwidth(500);   headerlabel.settext('please add text')    //set selection columns   var columnspanel = app.createhorizontalpanel().setid("columnspanel");   var columnname = app.createtextbox().settext("name");   var columntype = app.createlistbox();   var columnlabel = app.createlabel("1");   var columndelhandler = app.createserverclickhandler("columndel").addcallbackelement(hidinstallcolumns);    var columndelbutton = app.createbutton().settext("x").addclickhandler(columndelhandler);     columntype.additem("1");   columntype.additem("2");   columntype.additem("3");   columntype.additem("4");     columnspanel.add(columnlabel);    columnspanel.add(columnname);   columnspanel.add(columntype);  columnspanel.add(columndelbutton);   //       var addcolumnspanel = app.createhorizontalpanel().setid("addcolumnspanel");   var addbuttonhandler = app.createserverclickhandler("addcolumn").addcallbackelement(hidinstallcolumns);    var addbutton = app.createbutton().setid("btnaddcolumn").settext("add column").addclickhandler(addbuttonhandler);      addcolumnspanel.add(addbutton);      columngrid.setwidget(0, 0, columnspanel);   scroller.add(columngrid);   scroller.setheight(appheight-80);   maingrid.setwidget(0, 0, headerlabel);   maingrid.setwidget(1, 0, scroller);   maingrid.setwidget(2, 0, addcolumnspanel);    panel.add(maingrid);    app.add(panel);   ss.show(app);     logger.log("fully done");   return app; }    function addcolumn(e) {    var app =uiapp.getactiveapplication();    var mybutton = app.getelementbyid("btnaddcolumn");    mybutton.setenabled(false);    var columnrownumbers =  parsefloat(e.parameter.hidinstallcolumns);    logger.log("printcolumns");    logger.log(columnrownumbers);    columnrownumbers++;    logger.log(columnrownumbers);    var mytarg = app.getelementbyid("hidinstallcolumns");    mytarg.settext(columnrownumbers.tostring());   var delhidstr = "del" + columnrownumbers.tostring();   logger.log(delhidstr);     var columnnum =app.createhidden(delhidstr.tostring(),columnrownumbers).setid("columnnum");   var columngrid = app.getelementbyid('columngrid');   var columnspanel = app.createhorizontalpanel().setid("columnspanel");   var columnname = app.createtextbox().settext("name");   var columntype = app.createlistbox();   var columnlabel = app.createlabel(columnrownumbers);   app.add(columnnum);   var columndelhandler = app.createserverhandler("columndel").addcallbackelement(columnnum);   var columndelbutton = app.createbutton().settext("x").addclickhandler(columndelhandler);     columntype.additem("1");   columntype.additem("2");   columntype.additem("3");   columntype.additem("4");    columnspanel.add(columnlabel);   columnspanel.add(columnname);   columnspanel.add(columntype);    columnspanel.add(columndelbutton);   columngrid.resize(columnrownumbers, 1);    var location = columnrownumbers;   location = location -1;   columngrid.setwidget(location ,0,columnspanel);   mybutton.setenabled(true);   return app;    }    function columndel(eventinfo) {   var app =uiapp.getactiveapplication();   logger.log(eventinfo.parameter.columnnum); //keeps getting undefined   logger.log(parsefloat(eventinfo.parameter.columnnum)); //keeps getting nan } 

var columnnum has no .setname()