steppers.js

// (cos allows smooth transitions from 0->1->0)

// 0 -> 1 stepped sin frequency from 1 -> 5
function stepper(i){
  var t = 2*Math.PI* ~~(i * 10);
  return Math.cos(i*10*t)
}


// generalised version
// stepper = generateStepper(5,1)
function generateStepper(steps, initial){
  var c = steps * initial * 2 * Math.PI;
  return function(i){
    return Math.cos(~~(i * steps) * i * c)
  }
}