I am working on a web page in Bootstrap 4, that has sections with light and dark backgrounds and a fixed navbar. The navbar is dark (has the css class bg-dark) and, while it is easily visible against the light sections, it is indistinguishable against the dark ones.
I have added Bootstrap's scroll-spy to the page, but what it does is add the active class to the navbar items, as seen below:
.page-section {
padding: 70px 10px
}
.page-section.bg-dark * {
color: #fff;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
<body data-spy="scroll" data-target=".navbar" data-offset="15">
<nav class="navbar navbar-expand-sm navbar-dark bg-dark fixed-top">
<ul class="navbar-nav">
<li class="nav-item">
<a class="nav-link" href="#section1">Section 1</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section2">Section 2</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section3">Section 3</a>
</li>
</ul>
</nav>
<div id="section1" class="container-fluid bg-light page-section">
<h1>Section 1</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section2" class="container-fluid bg-dark page-section">
<h1>Section 2</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section3" class="container-fluid bg-light page-section">
<h1>Section 3</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
</body>
How can I change the navbar's navbar-dark bg-dark to navbar-light bg-light when the user reaches div with id section3 or (even better) with class bg-light?
There's no built-in way to change the target of the active class, so you're left with a javascript option. Fortunately, Bootstrap 4 does provide an event that gets triggered when a new active item is set. One odd quark with it is that the documentation suggests you can add the listener event to the element with data-spy. This does not work. You have to add it to the window object (https://stackoverflow.com/a/48694139/854246). Here's a code snippet:
$(window).on('activate.bs.scrollspy', function (e,obj) {
// spy changes to the last item at the end of the page,
// so we want to avoid changing the class at this point.
// Spy still works, but we want the class to be based on
// whatever block was closest.
// https://stackoverflow.com/a/40370876/854246
if ((window.innerHeight + window.pageYOffset) >= document.body.offsetHeight) {
return;
}
// Here we detect the targets class. I'm just using bg-
// light. Not the most robust solution, but it can be
// tweaked.
var isBGLight = $(obj.relatedTarget).hasClass('bg-light');
// note that navbar needs two classes to work. If you
// only set bg-light/bg-dark, the link text color doesn't
// change.
$('.navbar').toggleClass('navbar-dark bg-dark', isBGLight)
.toggleClass('navbar-light bg-light', !isBGLight);
});
.page-section {
padding: 70px 10px
}
.page-section.bg-dark * {
color: #fff;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
<body data-spy="scroll" data-target=".navbar" data-offset="15">
<nav class="navbar navbar-expand-sm navbar-dark bg-dark fixed-top">
<ul class="navbar-nav">
<li class="nav-item">
<a class="nav-link" href="#section1">Section 1</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section2">Section 2</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section3">Section 3</a>
</li>
</ul>
</nav>
<div id="section1" class="container-fluid bg-light page-section">
<h1>Section 1</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section2" class="container-fluid bg-dark page-section">
<h1>Section 2</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section3" class="container-fluid bg-light page-section">
<h1>Section 3</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
</body>
I would make this a stack snippet, but Stack Overflow doesn't like it when you listen to events on the window object for security reasons (sandboxed iframe and whatnot), so here is a fiddle demonstrating this solution: Apparently it does support it. It just doesn't like when you use console.log
https://jsfiddle.net/jmarikle/jzg7ok0v/
here a test with you need, but for scroll for 1 px and after begining the change for some states. sorry my bad english.
https://codepen.io/jhonycertz/pen/eQPbXy
$(window).scroll(function() {
var isScrolled = $(document).scrollTop() > 1;
$('.menu').toggleClass('nav_white', isScrolled);
$(window).on('activate.bs.scrollspy', function (e,obj) {
if ((window.innerHeight + window.pageYOffset) >= document.body.offsetHeight) {
return;
}
var Transparent = $(obj.relatedTarget).hasClass('nav_transparent');
var White = $(obj.relatedTarget).hasClass('nav_white');
var Blue = $(obj.relatedTarget).hasClass('nav_blue');
$('.nav').toggleClass('nav_transparent', Transparent, !White, !Blue)
.toggleClass('nav_white', White, !Transparent, !Blue)
.toggleClass('nav_blue', Blue, !Transparent, !White);
});
});
.page-section {
padding: 70px 10px
}
.move{
background-color:#000
}
.page-section.bg-dark * {
color: #fff;
}
.transparent{
background-color:green;
}
.nav_transparent{background-color:yellow;}
.nav_white{background-color:grey;}
.nav_blue{background-color:black;}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
<body data-spy="scroll" data-target=".nav" data-offset="15">
<nav class="menu nav navbar navbar-expand-sm nav_transparent fixed-top">
<ul class="navbar-nav">
<li class="nav-item ">
<a class="nav-link" href="#section">Section 0</a>
</li>
<li class="nav-item d-none">
<a class="nav-link" href="#section1">Section 1</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section2">Section 2</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section3">Section 3</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section4">Section 4</a>
</li>
</ul>
</nav>
<div id="section" class="container-fluid bg-light page-section">
<h1>Section 0</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section1" class="container-fluid bg-light page-section nav_transparent">
<h1>Section 1</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section2" class="container-fluid bg-light page-section nav_blue">
<h1>Section 2</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section3" class="nav_white container-fluid bg-dark page-section">
<h1>Section 3</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section4" class="nav_blue container-fluid bg-light page-section">
<h1>Section 4</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
</body>
Use js code for toggle class
$(window).on('activate.bs.scrollspy', function (e,obj)
{
if(document.querySelector(obj.relatedTarget).classList.contains('bg-light'))
{
$('.navbar').removeClass("navbar-dark bg-dark");
$('.navbar').addClass("bg-light navbar-light" );
}
else
{
$('.navbar').removeClass("bg-light navbar-light");
$('.navbar').addClass( "navbar-dark bg-dark" );
}
});
.page-section {
padding: 70px 10px
}
.page-section.bg-dark * {
color: #fff;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
<body data-spy="scroll" data-target=".navbar" data-offset="15">
<nav class="navbar navbar-expand-sm navbar-dark bg-dark fixed-top">
<ul class="navbar-nav">
<li class="nav-item">
<a class="nav-link" href="#section1">Section 1</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section2">Section 2</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#section3">Section 3</a>
</li>
</ul>
</nav>
<div id="section1" class="container-fluid bg-light page-section">
<h1>Section 1</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section2" class="container-fluid bg-dark page-section">
<h1>Section 2</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
<div id="section3" class="container-fluid bg-light page-section">
<h1>Section 3</h1>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
<p>Try to scroll this section and look at the navigation bar while scrolling! Try to scroll this section and look at the navigation bar while scrolling!</p>
</div>
</body>
