B2G/gecko/browser/components/tabview/groupitems.js
//          numbers to index from the end (-1 is the last child)
numbers to index from the end (-1 is the last child)
numbers to index from the end ( - 1 is the last child )
function GroupItem_getChild(index) {
    if (index < 0)
      index = this._children.length + index;
    if (index >= this._children.length || index < 0)
      return null;
    return this._children[index];
  }
function GroupItem_getChild ( index ) { if ( index < 0 ) index = this . _children . length + index ; if ( index >= this . _children . length || index < 0 ) return null ; return this . _children [ index ] ; }
numbers to index from the end (-1 is the last child)
numbers to index from the end ( - 1 is the last child )