webix.confirm in onBeforeDeleteFile - How can I fired SeverSide function?

Webix JS
#1

In onBeforeDeleteFile I want to ask the user to confirm the deletion. That what I have now.
Now I want counting the files and folders before I confirm the deletion. The user should be inform about that.
How can I fired the serverside function from the onBeforeDeleteFile?

#2 
{
   on: {
      onBeforeDeleteFile: function(id){
         var that = this;
         webix.ajax(...).then(function() {
            if(condition) {
               webix.confirm("Please confirm", "confirm-warning", function(result){
                  if(result) that.deleteFile(id);
               });
            }
         });
         return false;
      }
   }
}
#3

My code:

$$(“files”).attachEvent(“onBeforeDeleteFile”,function(id){
webix.ajax().post(page+"?action=removecount&source="+id, function(text, data, xhr){
dataJson = data.json();
countFiles=0;
countFolders=0;
isCount=false;
for(var i = 0; i < dataJson.length; i++) {
var obj = dataJson[i];
if(obj.data.hasOwnProperty(“files_count”) && obj.data.hasOwnProperty(“folders_count”)) {
countFiles += obj.data.files_count;
countFolders += obj.data.folders_count;
isCount=true;
} else {
countFiles += 1;
}
};
if(isCount) {
strText = “Delete “+countFiles+” File(s) and “+countFolders+” Folder(s)?”;
} else if(dataJson.hasOwnProperty(“type”)) {
if(dataJson.type == “removefolder”){
strText = “Delete Folder(s)?”;
} else {
strText = “Delete File(s)?”;
}
} else {
strText = “Delete File(s)?”;
}
webix.confirm({
text: strText,
type:“confirm-warning”,
callback:function(res){
if(res){
$$(“files”).deleteFile(id);
}
webix.callEvent(“onClick”, []);
}
});
});
return false;
});

This is good for me.

But on which place I place the progress functions?
The response time is to long without disable the input.

#4

you need to show progress just before ajax operation and hide progress on success or error.