code: function setLeft(x) {
              // Only if the scroll is not what it was last time we did this.
              if (x != lastOffsetLeft) {
                  // Move the target element horizontally relative to its original
                  // horizontal position.
                  target.css('left', offsetLeft - x);
  
                  // Hold the last horizontal position set.
                  lastOffsetLeft = x;
              }
          }
docs: Moves the target element left or right relative to the horizontal scroll position.