导航条吸顶效果

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <title></title>
      <script src="http://cdn.static.runoob.com/libs/jquery/2.1.1/jquery.min.js"></script>
    </head>
    <body>
        <div class="portalHeaderLink" id="nav">
             <a >我要开店</a>
            <a >我要做代理</a>
            <a >登录</a>
        </div>    
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    </body>
    <style>
        *{margin:0;padding:0;}
        .portalHeaderLink{background:red;position:fixed;top:0;width:100%;height:50px;line-height: 50px;}    
        .portalHeaderLink a{color:#fff;}    
        .navFixed{background:blue;}    
    </style>
    <script>
         window.onload = function(){       
        $(window).scrollTop(0)
        
            var $window = $(window);
            var $nav = $('#nav');
            var navTop = $nav.offset().top + $nav.height();
            $window.scroll(function () {
                var scrollTop = $(document).scrollTop();
                if (scrollTop >= navTop) {
                    if (!$nav.hasClass('fixed')) {
                    $nav.addClass('fixed').css('display', 'none').slideDown(300);
                    $nav.addClass('navFixed')
                }
            } else {
                $nav.removeClass('fixed');
                $nav.removeClass('navFixed')
                    
                }
                ;
            });
        }
        
    </script>
</html>

ps:参考了别人的代码,但是在此基础上面做了一些修改,当滚动到下面刷新页面的时候,背景色仍然是蓝色。

原文地址:https://www.cnblogs.com/Ljshu/p/7607927.html