<script>
function slideup(){
t = document.querySelector(".slide");
t.scrollTop -= t.offsetHeight;
}
function slidedown(){
t = document.querySelector(".slide");
t.scrollTop += t.offsetHeight;
}
</script>
<i class="icon icon-up" onclick="slideup()"></i>
<div class="slider" style="overflow-y: auto">
...
</div>
<i class="icon icon-down" onclick="slidedown()"></i>