code: function(index, node = this.fch) {
                  if(node.par !== this)
                      node = this.fch;
  
                  let first = node;
                  let i = 0;
                  while (node && node != first) {
                      if (i++ == index)
                          return node;
                      node = node.nxt;
                  }
  
                  return null;
              }
docs: Gets the child at index.
  
  @param      {number}  index   The index