固定导航，可以鼠标上划显示，下滑隐藏

 

function Navigater(obj) {
    var dom = document.getElementById(obj.dom);
    this.slide = function() {
        window.onmousewheel = function(e) {
            e = e || window.event;
            console.log(document.body.scrollTop);
            console.log(dom);
            // 判断鼠标是上滑动，还是下滑动
            if (e.wheelDelta) { // ie,google
                if (e.wheelDelta > 0) {
                    dom.setAttribute('class', 'byq_navigater show');
                } else if (e.wheelDelta < 0) {
                    dom.setAttribute('class', 'byq_navigater');
                }
            } else if (e.detail) { // firefox
                if (e.detail > 0) {
                    dom.setAttribute('class', 'byq_navigater show');
                } else if (e.detail < 0) {
                    dom.setAttribute('class', 'byq_navigater');
                }
            }
        }
    }
}