code: function () {
                          var acc = 0;
                          for (var i = 0; i < this.diffs_x.length; i++) {
                              acc += (this.diffs_x[i] / this.times_x[i]) * 1000 / 3;
                          }
                          return acc;
                      }
docs: Returns the scroll momentum in fractional page widths per second. (fpw/s * page width = px/s)