html,body {height:100%;}
body {margin:0px;}
div {height:100%;}

<div style="background:#FEE;"></div>
<div style="background:#EFE;"></div>
<div style="background:#EEF;"></div>
<div style="background:red;"></div>

document.addEventListener("DOMContentLoaded", function() {
 var body = document.body,
 html = document.documentElement;
 var itv, height = document.body.offsetHeight;
 var page = scrollTop() / height | 0;
 //窗口大小改变事件
 addEventListener("resize", onresize, false);
 onresize();
 //滚轮事件
 document.body.addEventListener(
 "onwheel" in document "wheel" : "mousewheel",
 function(e) {
  clearTimeout(itv);
  itv = setTimeout(function() {
  var delta = e.wheelDelta / 120 || -e.deltaY / 3;
  page -= delta;
  var max = (document.body.scrollHeight / height | 0) - 1;
  if (page < 0) return page = 0;
  if (page > max) return page = max;
  move();
  }, 100);
  e.preventDefault();
 }
 );
 //平滑滚动
 function move() {
 var value = height * page;
 var diff = scrollTop() - value;
 (function callee() {
  diff = diff / 1.2 | 0;
  scrollTop(value + diff);
  if (diff) itv = setTimeout(callee, 16);
 })();
 };
 //resize事件
 function onresize() {
 height = body.offsetHeight;
 move();
 };
 //获取或设置scrollTop
 function scrollTop(v) {
 if (v == null) return Math.max(body.scrollTop, html.scrollTop);
 else body.scrollTop = html.scrollTop = v;
 };
});