code: function getRelatives(slideePos) {
              slideePos = within(isNumber(slideePos) ? slideePos : pos.dest, pos.start, pos.end);
  
              var relatives = {},
                  centerOffset = forceCenteredNav ? 0 : frameSize / 2;
  
              // Determine active page
              if (!parallax) {
                  for (var p = 0, pl = pages.length; p < pl; p++) {
                      if (slideePos >= pos.end || p === pages.length - 1) {
                          relatives.activePage = pages.length - 1;
                          break;
                      }
  
                      if (slideePos <= pages[p] + centerOffset) {
                          relatives.activePage = p;
                          break;
                      }
                  }
              }
  
              // Relative item indexes
              if (itemNav) {
                  var first = false,
                      last = false,
                      center = false;
  
                  // From start
                  for (var i = 0, il = items.length; i < il; i++) {
                      // First item
                      if (first === false && slideePos <= items[i].start) {
                          first = i;
                      }
  
                      // Centered item
                      if (center === false && slideePos - items[i].size / 2 <= items[i].center) {
                          center = i;
                      }
  
                      // Last item
                      if (i === items.length - 1 || (last === false && slideePos < items[i + 1].end)) {
                          last = i;
                      }
  
                      // Terminate if all are assigned
                      if (last !== false) {
                          break;
                      }
                  }
  
                  // Safe assignment, just to be sure the false won't be returned
                  relatives.firstItem  = isNumber(first) ? first : 0;
                  relatives.centerItem = isNumber(center) ? center : relatives.firstItem;
                  relatives.lastItem   = isNumber(last) ? last : relatives.centerItem;
              }
  
              return relatives;
          }
docs: Return relative positions of items based on their visibility within FRAME.
  
  @param {Int} slideePos Position of SLIDEE.
  
  @return {Void}