code: function getUniqueSectionAnchor(anchor) {
  
              var base_anchor = anchor,
                  numeric_suffix = 0;
  
              while (used_section_anchors.indexOf(anchor) !== -1) {
                  anchor = base_anchor + "_" + ++numeric_suffix;
              }
  
              used_section_anchors.push(anchor);
              return anchor;
          }
docs: Assures section anchor to be unique
  @param {string} anchor
  @returns {string}
  @todo dry?