Why is onBeforeAjax invoked several times for one request?

Webix JS
#1

I have following code

webix.attachEvent("onBeforeAjax", function(mode, url, data, request, headers) {
    console.log("url: " + url);
});

When arise any request i see several lines in my logs, but browser shows only one request. Why so?

#2

Not sure. Normally it must one onBeforeAjax call for one request.

It possible that code aborts XHR requests ( for example if you are calling some.load(url); some.clearAll();, such code will start request, call onBeforeAjax and abort the request. As result there will be onBeforeAjax call, but there will not be a real request.

#3

How can i write some code which will be invoked only once for one real request?

#4

May be it will useful for someone, I’ve found solution as redefine send message in XMLHttpRequest prototype