loader.js

var loadData : function( urlEndpoint, callback ){
  var fullPath = this.baseUrl + urlEndpoint,
      encodedString = utf8ToBase64( fullPath ),
      $deferred;

  if( typeof fbiApiHelper.cacheData[ encodedString ] !== 'undefined' ){
      if( typeof fbiApiHelper.cacheData[ encodedString ].readyState !== 'undefined' ){
          // XHR object, do as ususal
          fbiApiHelper.cacheData[ encodedString ].done( function( response ){
              callback.call( this, response );
          } );

          return fbiApiHelper.cacheData[ encodedString ];
      } else {
          // Not an XHR object, data is loaded
          callback.call( this, fbiApiHelper.cacheData[ encodedString ] );
          $deferred = $.Deferred();
          $deferred.resolve( fbiApiHelper.cacheData[ encodedString ] );

          console.log( 'Loaded ' + fullPath + ' from cache' );
          return $deferred.promise();
      }
  }

  var xhr = $.ajax({
      url : fullPath,
      method : 'GET',
      dataType : 'jsonp',
      jsonp: '_jsonp'
  });

  fbiApiHelper.cacheData[ encodedString ] = xhr;

  xhr.done( function( response ){
      fbiApiHelper.cacheData[ encodedString ] = response;
      callback.call( this, response );
  } );

  xhr.fail( function( jqXHR, textStatus ) {
      console.log( 'Request failed: ' + textStatus );
  });

  return xhr;
};