Change navbar background color on page scroll

Question

Im having trouble getting my fixed top navbar to change background-color when I scroll the page.

Here is the function in JS:

$(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');
            }
        });
    }
 });

This is a file called " custom.js " and loaded at the bottom of the page AFTER I load bootstrap and jquery ( custom.js is in the same folder as index.html )

<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>

Here is the html navbar:

<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>

And then only css I have for navbar background color change:

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

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

Answer 1

This is what your current function and css does on a page that has a <div> with id=startchange . On page load the navbar is not transparent. As soon as you scroll the navbar becomes transparent (border still visible) and once the <div> with id=startchange passes the top of the page you navbar becomes non transparent again.

If you make your css more specific you can get the navbar to be transparent to start with no border (at larger screen sizes, you might want to look at how its styled for smaller screens too).

 $(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

Change value 50 as needed, 50px is page position after scroll

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

Answer 3

This way is very easy;

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

Answer 4

this is the simplest way to do it using pure JavaScript HTML DOM set the nav tag id to id="navbar" and also depending on where are you going to place your js code if you are going to apply it on the same page place the below code inside the script tags other wise just paste the code as is in your js file the navbar background color is transparent and onscroll the navbar change to red

 // 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; }

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