javascript - 为什么我无法更改幻灯片导航栏背景的宽度？

Question

所以有我的导航栏代码。我想在菜单上制作黑色背景，同时从顶部向下滑动一点，我可以这样做吗？我试图用 .shrink 类的宽度在 css 中做一些事情，但它什么也没改变。您还可以建议我如何在向下滑动时更改导航栏中徽标的位置？我将在图片中向您展示我希望它的外观。

https://ibb.co/cCh08RD - 这是图片，所以占位符是导航栏中徽标的位置。我希望它在滑动时降低，就像我试图绘制它一样，在徽标的位置我想显示菜单图片 - 类似于这 3 行。我也厌倦了画出我想要的宽度。

$(window).on('scroll', function() {
    if ($(window).scrollTop()) {
        $('nav').addClass('shrink');

    } else {
        $('nav').removeClass('shrink');
    }
});

.background {
    background-image: url('../images/img1-header.png');
    background-repeat: no-repeat;
    background-size: cover;
    background-position: center;
    height: 650px;
    width: 100%;
}
#siteNav {
    width: 100%;
    top: 0;
    left: 0;
    transition: 0.3s;
    display: flex;
    flex-direction: row;
    justify-content: center;
    padding-top: 20px;
    padding-bottom: 20px;
}
.shrink {
    background: rgba(32, 32, 32);
    height: 50px;
    position: fixed;
}
.shrink .logo {
    transition: 0.3s;
    display: flex;
    height: 38px;
}
#siteNav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
}
#siteNav ul li {
    list-style: none;
    border-right: 1px solid #fafafa;
    padding-top: 10px;
}
#siteNav ul li a {
    padding: 0 30px;
    text-decoration: none;
    transition: 0.3s;
    color: #000000;
}
#siteNav ul li:last-child {
    border-right: none;
}
header h1 {
    text-align: center;
    font-family: 'Homenaje', sans-serif;
    color: #000000;
    font-size: 58px;
    padding-top: 130px;
    letter-spacing: 3px;
}

header h1 a {
    color: #383838;
}

<div class="background">
            <nav id="siteNav">
                <img class="logo" src="http://placehold.it/40" alt="">
                <ul>
                    <li><a href="#mission">MISSION</a></li>
                    <li><a href="#clients">CLIENTS</a></li>
                    <li><a href="#products">PRODUCTS</a></li>
                    <li><a href="#contact">CONTACT</a></li>
                </ul>
            </nav>
            <header>
                <div>
                    <h1>aaaaaaa <br><a>aaaaaaaaa</a></br>
                    </h1>
                </div>
            </header>
        </div>

标签： javascriptjqueryhtmlcss

Answer 1

 function sticktothetop() {
    var window_top = $(window).scrollTop();
    var top = $('#stick-here').offset().top;
    if (window_top > top) {
        $('#stickThis').addClass('stick');
        $('#stick-here').height($('#stickThis').outerHeight());
    } else {
        $('#stickThis').removeClass('stick');
        $('#stick-here').height(0);
    }
}
$(function() {
    $(window).scroll(sticktothetop);
    sticktothetop();
});

#stickThis {
    padding: 20px;
    background-color: #ccc;
    font-size: 1.5em;
    width: 100%;
    text-align: center;
    font-weight: bold;
}
#stickThis.stick {
    margin-top: 0;
    padding: 5px;
    position: fixed;
    top: 0;
    text-align: left;
    z-index: 9999;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.0.0/jquery.min.js"></script>
<div id="stick-here"></div>
<div id="stickThis">Sticky note</div>
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