//非FF
  //event.wheelDelta
  // 正数:向上滚动，负数：向下滚动
  // 滚动一次值120
  document.body.onmousewheel = function (event) {
    event = event || window.event;
    log(‘onmousewheel‘);
    log(event);
    log(‘event.detail=‘ + event.detail);//0
    log(‘event.wheelDelta=‘ + event.wheelDelta);
  };
  //FF
  //  event.detail
  //  正数：向下滚动，负数：向上滚动
  //  向上滚动一页值为-32768，向下滚动一页值为+32768，其他值代表滚动的行数, 方向代表了数值的正负号
  //  受信任的事件是不会给detail赋值0
  document.body.addEventListener("DOMMouseScroll", function (event) {
    log(‘DOMMouseScroll‘);
    log(event);
    log(event.detail);
  });
  function log(arg) {
    window.console && window.console.log(arg);
  }