dynamically generated animated setter

dynamic.js

define([
'/dev/js/main.js',
'/dev/js/types.js',
rmod('common')],
function(main, types, common) {
  return {
    animated_setter: function(obj, property, getter, setter) {
      return function(to, animated, easing, callback) {
        if(common.is_false(animated)) {
          return setter(to);
        }
        var from_obj = {};
        from_obj[property] = getter();
        var to_obj = {};
        to_obj[property] = to;
        var last = null;
        $(from_obj).animate(to_obj, {
          step:function(now, fx) {
            if(last === null
              || (from_obj[property] > to_obj[property] && now < last)
              || (from_obj[property] < to_obj[property] && now > last)) {
              last = now;
              setter(now);
            }
          },
          easing: easing,
          duration: animated,
          complete: function(fx) {
            setter(to);
            if(!common.is_false(callback)) {
              callback();
            }
          }
        });
      }
    }
  };
});