ofMap JS implementation

//http://www.openframeworks.cc/documentation/math/ofMath.html#show_ofMap
function ofMap(value, r1a, r1b, r2a, r2b, clamp){
  if (clamp && value<=r1a)
    return r2a;
  if (clamp && value>=r1b)
    return r2b;
  var r1 = r1b-r1a;
  var r2 = r2b-r2a;
  return r2a+(value-r1a)*r2/(r1b-r1a)
}