code: function polygonCopy(polygon, i,j,targetPoly){
      var p = targetPoly || [];
      polygonClear(p);
      if (i < j) {
          // Insert all vertices from i to j
          for(var k=i; k<=j; k++){
              p.push(polygon[k]);
          }
  
      } else {
  
          // Insert vertices 0 to j
          for(var k=0; k<=j; k++){
              p.push(polygon[k]);
          }
  
          // Insert vertices i to end
          for(var k=i; k<polygon.length; k++){
              p.push(polygon[k]);
          }
      }
  
      return p;
  }
docs: Copy the polygon from vertex i to vertex j.
  @method copy
  @param  {Number} i
  @param  {Number} j
  @param  {Polygon} [targetPoly]   Optional target polygon to save in.
  @return {Polygon}                The resulting copy.