代码成长记录之页面滚动焦点图

$(function(){
var scrollEvent = function(){
$('.boxer').each(function(){
var $this = $(this);
var height =  $this.offset().top;
var windowHeight = $(window).scrollTop();
var absHeight = height-windowHeight;

var n = $this.index();
if(absHeight>=0&&absHeight<=200){
var $ul = $('.dot');
var $now = $ul.find('li.now');
$now.removeClass('now');
$('.dot li:eq('+n+')').addClass('now');    //注意  n是变量！！！！变量！！！变量！！！
}
});
};
//初始化事件
var main = function(){
$(window).bind('scroll',function(){
scrollEvent();
})
}
main();
})