JS field rendering return standard field rendering

how can return the standard rendering of a field?

(function () {

    var readonlyFiledContext = {};
    readonlyFiledContext.Templates = {};
    readonlyFiledContext.Templates.Fields = {
        // Apply the new rendering for Age field on Edit forms
        "Title": {
            "EditForm": FieldTemplate
        }
    };

    SPClientTemplates.TemplateManager.RegisterTemplateOverrides(FiledContext);

})();

function FieldTemplate(ctx) {

     return ;
    }
}

It depends on the value I like to render the filed. When the value is not null then make it fancy and when it is equals “null” then render like the standard rendering. How I can in this code segment return the standard field rendering?

Thanks for help Stefan

The following example demonstrates how to render text field using default rendering template if value is not empty:

SP.SOD.executeFunc("clienttemplates.js", "SPClientTemplates", function() {


    SPClientTemplates.TemplateManager.RegisterTemplateOverrides({

      Templates: {

           Fields: {
               "ReqNo": {
                   EditForm: renderRegNo,
               }
           }
      }

    });

});

function renderRegNo(ctx){
  if(ctx.CurrentItem.RegNo.length == 0) {
       return "Request number is missing";
  }
  return SPFieldText_Edit(cxt); 
}

Note: it is assumed that the RegNo field is of Text type

clientforms.js contains the list of default field rendering templates (per field type):

var spfieldCtx = {
            Templates: {
                Fields: {
                    'Text': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_Default,
                        'EditForm': SPFieldText_Edit,
                        'NewForm': SPFieldText_Edit
                    },
                    'Number': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_Default,
                        'EditForm': SPFieldNumber_Edit,
                        'NewForm': SPFieldNumber_Edit
                    },
                    'Integer': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_Default,
                        'EditForm': SPFieldNumber_Edit,
                        'NewForm': SPFieldNumber_Edit
                    },
                    'Boolean': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_DefaultNoEncode,
                        'EditForm': SPFieldBoolean_Edit,
                        'NewForm': SPFieldBoolean_Edit
                    },
                    'Note': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldNote_Display,
                        'EditForm': SPFieldNote_Edit,
                        'NewForm': SPFieldNote_Edit
                    },
                    'Currency': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_Default,
                        'EditForm': SPFieldNumber_Edit,
                        'NewForm': SPFieldNumber_Edit
                    },
                    'File': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldFile_Display,
                        'EditForm': SPFieldFile_Edit,
                        'NewForm': SPFieldFile_Edit
                    },
                    'Calculated': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_Default,
                        'EditForm': SPField_FormDisplay_Empty,
                        'NewForm': SPField_FormDisplay_Empty
                    },
                    'Choice': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_Default,
                        'EditForm': SPFieldChoice_Edit,
                        'NewForm': SPFieldChoice_Edit
                    },
                    'MultiChoice': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_Default,
                        'EditForm': SPFieldMultiChoice_Edit,
                        'NewForm': SPFieldMultiChoice_Edit
                    },
                    'Lookup': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldLookup_Display,
                        'EditForm': SPFieldLookup_Edit,
                        'NewForm': SPFieldLookup_Edit
                    },
                    'LookupMulti': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldLookup_Display,
                        'EditForm': SPFieldLookup_Edit,
                        'NewForm': SPFieldLookup_Edit
                    },
                    'Computed': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPField_FormDisplay_Default,
                        'EditForm': SPField_FormDisplay_Default,
                        'NewForm': SPField_FormDisplay_Default
                    },
                    'URL': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldUrl_Display,
                        'EditForm': SPFieldUrl_Edit,
                        'NewForm': SPFieldUrl_Edit
                    },
                    'User': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldUser_Display,
                        'EditForm': SPClientPeoplePickerCSRTemplate,
                        'NewForm': SPClientPeoplePickerCSRTemplate
                    },
                    'UserMulti': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldUserMulti_Display,
                        'EditForm': SPClientPeoplePickerCSRTemplate,
                        'NewForm': SPClientPeoplePickerCSRTemplate
                    },
                    'DateTime': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldDateTime_Display,
                        'EditForm': SPFieldDateTime_Edit,
                        'NewForm': SPFieldDateTime_Edit
                    },
                    'Attachments': {
                        'View': RenderFieldValueDefault,
                        'DisplayForm': SPFieldAttachments_Default,
                        'EditForm': SPFieldAttachments_Default,
                        'NewForm': SPFieldAttachments_Default
                    }
                }
            }
        };