tag 滚动变换

/**
* 产品详情页滚动
*/
$(document).ready(function () {
$(window).scroll(function () {
var sectionArray = $('.cy-cp-intro-warp');
for(var i=0; i<sectionArray.length-1; i++){
var objP = $(sectionArray[i])
, objN = $(sectionArray[i+1]);
if($(window).scrollTop()>= (objP.offset().top-200)
&& $(window).scrollTop()<(objN.offset().top-200)){
$('.cy-cp-nav ul li').removeClass('active');
$($('.cy-cp-nav ul li')[i]).addClass('active');
}
}
});
});