/鼠标滚珠上下滑动/
var topx = 0
var status = 0;
$(window).bind('mousewheel DOMMouseScroll', function(event) {

var obj = $("p.sectionwrap");
**var num = obj.attr('data-num') * 1;
var winHeight = $(window).height();
if (event.originalEvent.wheelDelta > 0 || event.originalEvent.detail < 0) {** //向上滑动
    if (num > 0 && status == 0) {
        status = 1;
        topx = -(num - 1) * winHeight;
        obj.css('top', topx + "px");
        $('#zhuangt li').find('span').removeClass('select');
        $('#zhuangt li').eq(num - 1).find('span').addClass('select');
        
        setTimeout(function() {
            status = 0;
            obj.attr('data-num', num - 1);
            if (num === 4) {
                $('.nextbtn').find('i').attr('class', 'fa fa-angle-down');
            };
        }, 800);
    };
} else {
    if (num < 4 && status == 0) {
        status = 1;
        topx = -(num + 1) * winHeight;
        obj.css('top', topx + "px");
        $('#zhuangt li').find('span').removeClass('select');
        $('#zhuangt li').eq(num + 1).find('span').addClass('select');
        setTimeout(function() {
            status = 0;
            obj.attr('data-num', num + 1);
            
            if (num === 3) {
                $('.nextbtn').find('i').attr('class', 'fa fa-angle-up');
            };
        }, 800);
    };
}

});
不懂为什么加“originalEvent”，另外再问一下“*1”是有什么用？求大神解答。