It's a function used to emulate to scrollTo of library jQuery but not using jQuery, only use pure Javascript :).

goTo

function goTo(container, idElementTo, duration,last_difference){
  if (duration < 0) return;
  
  last_difference = typeof last_difference !== 'undefined' ? last_difference : -1;
  to = document.getElementById(idElementTo);
  
  var difference = to.offsetTop - container.scrollTop;
  var perTick = difference / duration * 10;
  
  if (last_difference === difference ) return;
  
  setTimeout(function() {
    container.scrollTop = container.scrollTop + perTick;
    if (container.scrollTop === to.offsetTop) return;
    goTo(container, to.id, duration - 10,difference);
  }, 10);
};

/* container: Is the element containing the element will to go,
   idElementTo: Is the id of element will to go,
   duration: Is the time at milliseconds for the transition,
   last_difference: Obvious,
   
   And then it would be used so: goTo(document.body,'myIdElement',500)
*/