未在jQuery中设置css属性

制作简单的parrallax，但不起作用。
未设置或访问css top属性…
如何设置视差使视差工作。。pz

<div class="bg">
<div class="container">
   <h1>Parallax Effect</h1>
   <p class="lead">goes here</p>

</div>
</div>

jQuery

function parallax(){
   var scrolled = $(window).scrollTop();
   $('.bg').css('top', -(scrolled * 0.3) + 'px');
   console.log($('.bg').css('top', -(scrolled * 0.3) + 'px'));
}

$(window).scroll(function(e){
   parallax();
});

---

尝试将parseInt添加到计算的滚动条中

function parallax(){
   var scrolled = $(window).scrollTop();
   $('.bg').css('top', parseInt(scrolled * 0.3 * -1) + 'px');
   console.log($('.bg').css('top', parseInt(scrolled * 0.3 * -1) + 'px'));
}

function parallax(){
   var scrolled = $(window).scrollTop();
   $('.bg').css('top', parseInt(scrolled * 0.3 * -1) + 'px');
   console.log($('.bg').css('top', parseInt(scrolled * 0.3 * -1) + 'px'));
}