docs/bundle.js
function point(that, t0, t1) {
  var x0 = that._x0,
      y0 = that._y0,
      x1 = that._x1,
      y1 = that._y1,
      dx = (x1 - x0) / 3;
  that._context.bezierCurveTo(x0 + dx, y0 + dx * t0, x1 - dx, y1 - dx * t1, x1, y1);
}
function point(that, t0, t1) {
  var x0 = that._x0,
      y0 = that._y0,
      x1 = that._x1,
      y1 = that._y1,
      dx = (x1 - x0) / 3;
  that._context.bezierCurveTo(x0 + dx, y0 + dx * t0, x1 - dx, y1 - dx * t1, x1, y1);
}
According to https://en.wikipedia.org/wiki/Cubic_Hermite_spline#Representations "you can express cubic Hermite interpolation in terms of cubic Bézier curves with respect to the four values p0, p0 + m0 / 3, p1 - m1 / 3, p1".