Unsolved JWT authenication in qml

[dsba]

Hi,
I am very much new to REST API, I tried Flickr Calls example that 's was given in book Qt5 Cadaques.
I faced two problems,

1. I could assign json object to listView model but this did not work
   for example:

In javascript function I am writing as
if(xhr.readyState === XMLHttpRequest.DONE)
      json = JSON.parse(xhr.responseText.toString())
      for(var i=0; i<json.length; i++) {
          view.model = json[i].id
      }
}

In ListView's Delegate:
delegate: Image {                      
             source: "/home/images/test_" + modelData.id + ".png
}

2. I have user name : "admin" and password: "123" receiving from end points
   I have created two textInput for user to enter his user name and password
   and writing javascript function called request

function request() {
        var xhr = new XMLHttpRequest();
        if(xhr.readyState === XMLHttpRequest.DONE) {
           var json = JSON.parse(xhr.responseText.toString())
}
       xhr.open("POST", url, true, "admin", "123") 
       xhr.send("userName=user&password=pwd");  /*sending entered text from textInput to http*/
}

This does not get authenticated and moves to next screen. What and where am I doing wrong.

Thanks in advance for the support and quick response