code: function polygonMakeCCW(polygon){
      var br = 0,
          v = polygon;
  
      // find bottom right point
      for (var i = 1; i < polygon.length; ++i) {
          if (v[i][1] < v[br][1] || (v[i][1] === v[br][1] && v[i][0] > v[br][0])) {
              br = i;
          }
      }
  
      // reverse poly if clockwise
      if (!isLeft(polygonAt(polygon, br - 1), polygonAt(polygon, br), polygonAt(polygon, br + 1))) {
          polygonReverse(polygon);
          return true;
      } else {
          return false;
      }
  }
docs: Make sure that the polygon vertices are ordered counter-clockwise.
  @method makeCCW