更改页面滚动上的导航栏背景颜色

Question

当我滚动页面时，我无法让固定的顶部导航栏更改background-color 。

这是JS中的函数：

$(document).ready(function(){       
    var scroll_start = 0;
    var startchange = $('#startchange');
    var offset = startchange.offset();
    if (startchange.length){
        $(document).scroll(function() { 
            scroll_start = $(this).scrollTop();
            if(scroll_start > offset.top) {
                $(".navbar").css('background-color', '#f0f0f0');
            } else {
                $('.navbar').css('background-color', 'transparent');
            }
        });
    }
 });

这是一个名为“ custom.js ”的文件，在我加载bootstrap and jquery后加载在页面底部（ custom.js与index.html位于同一文件夹中）

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<script src="custom.js"></script>

这是 html 导航栏：

<div class="container">
    <nav class="navbar navbar-default navbar-fixed-top">
        <div class="container-fluid">
            <div class="navbar-header ">                  
                <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbarNav">
                    <span class="sr-only">Toggle navigation</span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                </button>
            </div>

            <div id="navbarNav" class="navbar-collapse collapse ">
                <br/><br/>
                <ul class="nav navbar-nav navbar-right ">
                    <li><a href="#">ABOUT</a></li>
                    <li><a href="#">SERVICES</a></li>
                    <li><a href="#">CONTACT</a></li>
                    <li><a href="#">CALCULATORS</a></li>
                </ul>
            </div> 
        </div>
    </nav>
</div>

然后只有用于导航栏背景颜色更改的 css：

.navbar {
    background-color: transparent;
    border-color: transparent;
}

.navbar-toggle:hover, .navbar-default .navbar-toggle:focus{
    background-color: transparent !important;
}

Answer 1

这就是您当前的函数和 css 在具有id=startchange的<div>的页面上id=startchange 。 在页面加载导航栏不透明。 一旦您滚动导航栏变得透明（边框仍然可见），一旦带有id=startchange的<div>通过页面顶部，您的导航栏将再次变得不透明。

如果你让你的 css 更具体，你可以让导航栏透明，开始时没有边框（在较大的屏幕尺寸下，你可能还想看看它在较小屏幕上的样式）。

 $(document).ready(function(){ var scroll_start = 0; var startchange = $('#startchange'); var offset = startchange.offset(); if (startchange.length){ $(document).scroll(function() { scroll_start = $(document).scrollTop(); if(scroll_start > offset.top) { $(".navbar").css('background-color', '#f0f0f0'); } else { $('.navbar').css('background-color', 'transparent'); } }); } });

 .navbar.navbar-default.navbar-fixed-top { background-color: transparent; border-color: transparent; -webkit-transition: background-color 2s; /* Safari */ transition: background-color 2s; } .navbar-toggle:hover, .navbar-default .navbar-toggle:focus{ background-color: transparent !important; }

 <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous"> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script> <div class="container"> <nav class="navbar navbar-default navbar-fixed-top"> <div class="container-fluid"> <div class="navbar-header "> <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbarNav"> <span class="sr-only">Toggle navigation</span> <span class="icon-bar"></span> <span class="icon-bar"></span> <span class="icon-bar"></span> </button> </div> <div id="navbarNav" class="navbar-collapse collapse "> <br/><br/> <ul class="nav navbar-nav navbar-right "> <li><a href="#">ABOUT</a></li> <li><a href="#">SERVICES</a></li> <li><a href="#">CONTACT</a></li> <li><a href="#">CALCULATORS</a></li> </ul> </div> </div> </nav> <div id="page"> Page Top <br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br> <div id="startchange">Start Change Div</div> <br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br> Page Bottom </div> </div>

Answer 2

根据需要更改值50px是滚动后的页面位置

$(document).ready(function () {
                    $(window).scroll(function () {
                        if ($(window).scrollTop() >= 50) {
                            $(".navbar").css("background-color", "#222");
                        } else {
                            $(".navbar").css("background-color", "transparent");
                        }
                    });
                });

Answer 3

这种方式非常简单；

let blackToRed = [0,0,0,1];
$(document).ready(function(){
    $(document).scroll(function() {
        blackToRed[0] = window.scrollY;
        $("#item").css('color', 'rgba(' + blackToRed + ')');
    });
});

Answer 4

这是使用纯 JavaScript HTML DOM 执行此操作的最简单方法，将导航标记 id 设置为 id="navbar" 并且如果要将 js 代码应用到同一页面上，还取决于将其放置在何处在脚本标签内的代码下方，否则只需将代码按原样粘贴到您的 js 文件中，导航栏背景颜色是透明的，然后滚动导航栏更改为红色

 // When the user scrolls down 80px from the top of the document, resize the navbar's padding and the logo's font size window.onscroll = function() {scrollFunction()}; function scrollFunction() { if (document.body.scrollTop > 80 || document.documentElement.scrollTop > 80) { document.getElementById("navbar").style.backgroundColor = "red"; // document.getElementById("logo").style.fontSize = "25px"; } else { document.getElementById("navbar").style.backgroundColor = "transparent"; // document.getElementById("logo").style.fontSize = "35px"; } }

 * {box-sizing: border-box;} body { margin: 0; font-family: Arial, Helvetica, sans-serif; } #navbar { overflow: hidden; background-color: #f1f1f1; padding: 90px 10px; transition: 0.4s; position: fixed; width: 100%; top: 0; z-index: 99; } #navbar a { float: left; color: black; text-align: center; padding: 12px; text-decoration: none; font-size: 18px; line-height: 25px; border-radius: 4px; } #navbar #logo { font-size: 35px; font-weight: bold; transition: 0.4s; } #navbar a:hover { background-color: #ddd; color: black; } #navbar a.active { background-color: dodgerblue; color: white; } #navbar-right { float: right; } @media screen and (max-width: 580px) { #navbar { padding: 20px 10px !important; } #navbar a { float: none; display: block; text-align: left; } #navbar-right { float: none; }

 <div id="navbar"> <a href="#default" id="logo">CompanyLogo</a> <div id="navbar-right"> <a class="active" href="#home">Home</a> <a href="#contact">Contact</a> <a href="#about">About</a> </div> </div> <div style="margin-top:210px;padding:15px 15px 2500px;font-size:30px"> <p><b>changing nav bar on scroll.</b></p> <p>Scroll down to see the effect!</p> <p>Scroll to the top to remove the effect.</p> What is Lorem Ipsum? Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum. Why do we use it? It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like). </p> </div>