Some MVVM class based approach thing

create-user-view-model.js

// Imagine this is a starting page where the user creates their account
function CreateUserViewModel()
{ 
     // could be done via IoC to improve testability and reuseability
    var someAjaxService = {}; // Imagine it does something
    this.user = new User();
    
    var saveDataToServer = function() {
      var data = ko.toJS(this.user);
      someAjaxService.Post("/users", data);
    }
    
    this.createUser = function() {
      if(this.user.isValid()) {
        saveDataToServer();
      }
    }
}

user.js

function User() {
    this.id = ko.observable(0);
    this.name = ko.observable("default").extend({required: true, minLength: 10, maxLength: 30);
    this.email = ko.observable("not valid").extend({required: true, email: true });
}

view-user-view-model.js

// Assume this view model is on a page and the user is viewing their account
function ViewUserViewModel()
{
    var someAjaxService = {}; // Imagine it does something
    this.user = new User();

    var updateUserData = function(userData) {
      ko.merge(this.user, userData);
    }
    
    this.populateUserFromServer = function(userId) {
        someAjaxService.Get("/users", userId)
          .then(updateUserData);
    };    
}