How to use $.ajax request. How to use $.Deferred()

gistfile1.js

/**
 * submit function:
 * - take userToken as a input parameter
 * - request form schema with the userToken if it exists.
 * - display form schema on the page.
 */
 
<div id="message"></div>

function submit (data) {
  var request = $.ajax({
    type: 'POST',
    url: 'http://myserver.com/submit',
    data: data
  });
  
  request.done(function (message) {
    $('.message').html(message);
  });
}

gistfile2.js

/**
 * Add cross domain storage
 */

var Storage = function () {
  this.domainUrl = 'http://thirdparty.com/storage';
};

// GET the data saved in the crossdomain storage.
Storage.prototype.get = function (key, fn) {
  $.ajax({
    type : 'GET',
    url : this.domainUrl,
    data : { key : key }
  })
  .done(function (data) {
    fn(data);
  })
  .fail(function (error) {
    fn({error : true});
  });
}

// SAVE the data to the crossdomain storage.
Storage.prototype.set = function (key, value, fn) {
  $.ajax({
    type : 'POST',
    url : this.domainUrl,
    data : { 
      key : key,
      data : value
    }
  })
  .done(function (data) {
    fn();
  })
  .fail(function (error) {
    fn({error : true});
  });
}


/**
 * submit function.
 * If no input data, use the crossdomain data
 */
function submit (data) {
  if (!data) {
    var storage = new Storage();
    storage.get('data', function (data) {
      submit(data || {});
    });
  }
  else {
    // AJAX request.
  }
};

gistfile3.js

/**
 * User $.Deferred()
 */

var Storage = function () {
  this.domainUrl = 'http://thirdparty.com/storage';
};

// GET the data saved in the crossdomain storage.
Storage.prototype.get = function (key) {
  return $.ajax({
    type : 'GET',
    url : this.domainUrl,
    data : { key : key }
  });
}

// SAVE the data to the crossdomain storage.
Storage.prototype.set = function (key, value) {
  return $.ajax({
    type : 'POST',
    url : this.domainUrl,
    data : { 
      key : key,
      data : value
    }
  });
}



/**
 * submit function.
 * If no input data, use the crossdomain data
 */
function submit (data) {
  if (data) {
    var storage = new Storage();
    var getDfd = storage.get('user');
    getDfd.done(function (data) {
      submit(data || {})
    });
  };
  else {
    // AJAX request
  }
}