code: function DragDropTouch() {
              this._lastClick = 0;
              // enforce singleton pattern
              if (DragDropTouch._instance) {
                  throw 'DragDropTouch instance already created.';
              }
              // listen to touch events
              if ('ontouchstart' in document) {
                  var d = document, ts = this._touchstart.bind(this), tm = this._touchmove.bind(this), te = this._touchend.bind(this);
                  d.addEventListener('touchstart', ts);
                  d.addEventListener('touchmove', tm);
                  d.addEventListener('touchend', te);
                  d.addEventListener('touchcancel', te);
              }
          }
docs: Initializes the single instance of the @see:DragDropTouch class.