code: function refresh(entry) {
          if (entry !== freshEnd) {
            if (!staleEnd) {
              staleEnd = entry;
            } else if (staleEnd === entry) {
              staleEnd = entry.n;
            }
  
            link(entry.n, entry.p);
            link(entry, freshEnd);
            freshEnd = entry;
            freshEnd.n = null;
          }
        }
docs: makes the `entry` the freshEnd of the LRU linked list