How to call properties like methods in JavaScript

I downloaded the code from Git and here is the link https://github.com/MikeWasson/LocalAccountsApp

In this visual studio solution we have JavaScript file called app.js which has the following code.

function ViewModel() {
var self = this;
var tokenKey = 'accessToken';

self.result = ko.observable();
self.user = ko.observable();

self.registerEmail = ko.observable();
self.registerPassword = ko.observable();
self.registerPassword2 = ko.observable();

self.loginEmail = ko.observable();
self.loginPassword = ko.observable();

function showError(jqXHR) {
    self.result(jqXHR.status + ': ' + jqXHR.statusText);
    //self.loginPassword();
}

self.callApi = function () {
    self.result('');

    var token = sessionStorage.getItem(tokenKey);
    var headers = {};
    if (token) {
        headers.Authorization = 'Bearer ' + token;
    }

    $.ajax({
        type: 'GET',
        url: '/api/values',
        headers: headers
    }).done(function (data) {
        self.result(data);
    }).fail(showError);
}

self.register = function () {
    self.result('');

    var data = {
        Email: self.registerEmail(),
        Password: self.registerPassword(),
        ConfirmPassword: self.registerPassword2()
    };

    $.ajax({
        type: 'POST',
        url: '/api/Account/Register',
        contentType: 'application/json; charset=utf-8',
        data: JSON.stringify(data)
    }).done(function (data) {
        self.result("Done!");
    }).fail(showError);
}

self.login = function () {
    self.result('');

    var loginData = {
        grant_type: 'password',
        username: self.loginEmail(),
        password: self.loginPassword()
    };

    $.ajax({
        type: 'POST',
        url: '/Token',
        data: loginData
    }).done(function (data) {
        self.user(data.userName);
        // Cache the access token in session storage.
        sessionStorage.setItem(tokenKey, data.access_token);
    }).fail(showError);
}

self.logout = function () {
    self.user('');
    sessionStorage.removeItem(tokenKey)
   }
  }
     var app = new ViewModel();
     ko.applyBindings(app);

What I'm not able to understand that how come properties like

self.result, self.registerEmail, self.registerPassword/Password2, self.loginEmail, self.loginPassword 

became methods. Because when I type "self" followed by a dot the intellisense gives all the above mentioned "self" properties as methods. Like

  self.result(), self.registerPassword()

And obviously "ko" comes from Knockout.js library.

But when I try to imitate the same in my simple JavaScript code. It fails and I know it's not right to do it here

  var SomeObj = {
  ok : function()
   {
    var x = 10, y= 10, z;
    z = x+ y;
    return z;
   }
 }


  function ViewModel()
  {
     var self = this;
     self.result = SomeObj.ok();
     function xyz()
     {
        self.result();
         alert(5700);
     }
}

var v = new ViewModel();
alert(v.result());  

But how come object "self" has declared "result" as property and used it later like a method in app.js where as when I try

     alert(v.result());

in the alert statement It gives me an exception but if I do

     alert(self.result()); 

in app.js it gives me back "undefined" but why not an exception the way I get in my code.