Javascript is functional

catmullrom.js

var catmullRom = function(p0, p1, p2, p3, distance) {
  var points = [p0, p1, p2, p3],
    t = function(dest) {
      if (dest === 0) return 0;
      return Math.pow(
        Math.sqrt(
          Math.pow(points[dest].x - points[dest-1].x,2) + Math.pow(points[dest].y - points[dest-1].y,2) + Math.pow(points[dest].z - points[dest-1].z,2)
        ), 0.5) + t(dest-1);
    },
    t0 = t(0),
    t1 = t(1),
    t2 = t(2),
    t3 = t(3),
    innerdist = distance*(t2-t1) + t1,
    a1 = p0.clone()
      .multiplyScalar((t1 - innerdist)/(t1 - t0))
      .add(p1.clone().multiplyScalar((innerdist - t0)/(t1 - t0))),
    a2 = p1.clone()
      .multiplyScalar((t2 - innerdist)/(t2 - t1))
      .add(p2.clone().multiplyScalar((innerdist - t1)/(t2 - t1))),
    a3 = p2.clone()
      .multiplyScalar((t3 - innerdist)/(t3 - t2))
      .add(p3.clone().multiplyScalar((innerdist - t2)/(t3 - t2))),
    b1 = a1.clone()
      .multiplyScalar((t2 - innerdist)/(t2 - t0))
      .add(a2.clone().multiplyScalar((innerdist - t0)/(t2 - t0))),
    b2 = a2.clone()
      .multiplyScalar((t3 - innerdist)/(t3 - t1))
      .add(a3.clone().multiplyScalar((innerdist - t1)/(t3 - t1))),
    c = b1.clone()
      .multiplyScalar((t2 - innerdist)/(t2 - t1))
      .add(b2.clone().multiplyScalar((innerdist - t1)/(t2 - t1)));
  return c;
};