Javascript/scrollBy()

function scroll1(){
  window.scrollBy(0,350);
}
function scroll2(){
  window.scrollBy(0,-350);
}

var stopBtn = document.getElementById("stopBtn");
stopBtn.disabled = true;
function sample2Func(){
  scrollBy(0,2);
  var s2Btn = document.getElementById("s2Btn");
  s2Btn.disabled = true;
  stopBtn.disabled = false;
  var scroll = setTimeout("sample2Func()", 100);
  
  stopBtn.onclick = function(){
	clearTimeout(scroll);
	s2Btn.disabled = false;
	stopBtn.disabled = true;
  }
}