jquery change opacity and height on scroll

问题

I'm currently trying to write a little js. My navigation has a gradient set as background. I want the background to change in height and from a gradient to a flat color with 0.85 opacity (animated) when I scroll down a certain amount.

here's my js code

$(window).scroll(function(){
if  ($(window).scrollTop() >= 600){
     $('#navigation').css({height: '92px'});
} else {
     $('#navigation').css({height: '142px'});
    }
});     

here's the css

#navigation {

height: 142px;
width: 1350px;
position: fixed;
z-index: 2000;

background: -moz-linear-gradient(top,  rgba(0,0,0,0.75) 0%, rgba(0,0,0,0) 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,rgba(0,0,0,0.75)), color-stop(100%,rgba(0,0,0,0))); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top,  rgba(0,0,0,0.75) 0%,rgba(0,0,0,0) 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top,  rgba(0,0,0,0.75) 0%,rgba(0,0,0,0) 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(top,  rgba(0,0,0,0.75) 0%,rgba(0,0,0,0) 100%); /* IE10+ */
background: linear-gradient(to bottom,  rgba(0,0,0,0.75) 0%,rgba(0,0,0,0) 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#bf000000', endColorstr='#00000000',GradientType=0 ); /* IE6-9 */

}

hope someone can help me

回答1:

Your code is good !!

Just create two separate class and replace your $('#navigation').css({height: '92px'}); by $('#navigation').addClass("flatColored"); and $('#navigation').removeClass("flatColored"); in the 'else'.

instead of having #navigation{ ...} in your css, use .gradientColored{...} .flatcolored{...}

and in your html : <div id="navigation" class="gradientColored">...</div>

Override the background properties in the 'flatColored class.

Tested on chrome, based on your code. Works fine !

来源：https://stackoverflow.com/questions/16553444/jquery-change-opacity-and-height-on-scroll