<script>

window.onscroll = function(){
var scrollT = document.documentElement.scrollTop||document.body.scrollTop;
var scrollH = document.documentElement.scrollHeight||document.body.scrollHeight;
var clientH = document.documentElement.clientHeight||document.body.clientHeight
//console.log(scrollT +"+"+scrollH+"+"+clientH);
if(scrollT == scrollH - clientH){
console.log("到底部了");
}else if(scrollT == 0){
console.log("到頂部了");
}
}

</script>