Particle Tornado

How do I program (in javascript), a way to make a particle tornado?

I had the idea to make each particle rotate around the Y-Axis as they rise, but I'm not sure where to start on that since I never programmed for particles and the example document in Unity doesn't work for somewhere?

You don't need to program anything, just play with the particle emitter and animator values, primarily the world rotation axis, plus velocity and force. You could also rotate the particle system itself, as long as "simulate in worldspace" is not checked.