How to get data when Ajax response

I post a picture on html like this

the picture was uploaded and the server response data, i will do something in js file like this

but the data is undefined,why?the doc

Посмотрите в консоли, что возвращает сервер, а также есть ли какие-то ошибки.

Kindly read through these request section in docs… You will understand. It’s not long…

No mistake. The server has returned data.

Found, there is an issue with it in code, use app event instead:

var app = new Framework7();

app.on('formAjaxSuccess', function (formEl, data, xhr) {
  // do something with response data

This work globally for all forms, how can i specify it for a particular form?