解决方法
jQuery将允许简洁的解决方案,同时隐藏大多数浏览器差异.这是一个快速模拟,让你开始：
<script type="text/javascript">
//when the DOM has loaded
$(document).ready(function() {
//attach some code to the scroll event of the window object
//or whatever element(s) see http://docs.jquery.com/Selectors
$(window).scroll(function () {
var height = $('body').height();
var scrollTop = $('body').scrollTop();
var opacity = 1;
// do some math here,by placing some condition or formula
if(scrollTop > 400) {
opacity = 0.5;
}
//set the opacity of div id="someDivId"
$('#someDivId').css('opacity',opacity);
});
});
</script>
也可以看看：
> jQuery
> Selectors
> CSS
> Events/Scroll
> CSS/ScrollTop
> CSS/ScrollLeft
