jQuery addClass example

Change class name on click in jQuery

HTML

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/css/bootstrap.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/js/bootstrap.min.js"></script>
	<nav class="navbar navbar-expand-lg navbar-light fixed-top">
			<div class="container">
				<a href="index.html" class="navbar-brand">
					<img src="img/mlogo.png" width="50" height="50" alt="" id="logo">  <span class="d-inline align-middle">Faculty Evaluation</span>
				</a>
				<button class="navbar-toggler" data-toggle="collapse" data-target="#navbarNav">
				<span class="navbar-toggler-icon"></span>
				</button>
				<div class="collapse navbar-collapse" id="navbarNav">
					<ul class="navbar-nav ml-auto">
						<li class="nav-item">
							<a href="#home" class="nav-link">Home</a>
						</li>
						<li class="nav-item">
							<a href="#services" class="nav-link">Services</a>
						</li>
						<li class="nav-item">
							<a href="#faq" class="nav-link">FAQ</a>
						</li>
						<li class="nav-item">
							<a href="#team" class="nav-link">Team</a>
						</li>
						<li class="nav-item">
							<a href="#contact" class="nav-link">Contact us</a>
						</li>
						<li class="nav-item">
							<a href="login.html" class="nav-link btn btn-outline-info px-4 mt-1"  data-toggle="modal" data-target="#loginModal1">Login</a>
						</li>
					</ul>
				</div>
			</div>
		</nav>

<div class="modal fade modal-open" role="dialog" id="loginModal1">
  <div class="modal-dialog">
    <div class="modal-content">
      <div class="modal-header">
        <h3 class="modal-title">Modal Login Form</h3>
        <button type="button" class="close" data-dismiss="modal">&times;</button>
      </div>
      <div class="modal-body">
        <div class="form-group">
          <input type="text" name="" class="form-control" placeholder="Username">
        </div>

        <div class="form-group">
      ...

SCSS

// Global variables

$primary: #3292a6;
$primary-overlay:rgba(50,146,166,0.8);
$footer-color: #2c8192;

body{
	margin-top:  90px;
  height: 1000px;
}


.modal-open {
overflow-y: auto !important;
padding-right: 0 !important;
}
.modal-scrollbar-measure {

overflow: hidden;
}
.modal-open {
    overflow: scroll;
}

.link:link{
  text-decoration: none;
  color: black;
}

.link:hover{
  text-decoration: underline;
  color: black;
}

.link:visited {
    text-decoration: none;
    color: black;
}
.link{
  color: black;
}



// Styling for banner
.navbar{
	box-shadow:2px 2px 5px $primary;
	opacity: 0.9;
	background: #fff;
	padding-top: 15px;
 	padding-bottom: 15px;
 	transition: all 0.2s;

	.nav-item{
		font-size: 1.2rem;
		padding-right:10px;
		color: white;
	}

	.navbar-brand {
        font-size: 1.75em;
        transition: all 0.2s;
      }


} 

.navbar.compressed {
  padding-top: 10px;
  padding-bottom: 10px;
  // background: $primary;
  box-shadow:2px 2px 5px $primary;
	
  .nav-link , a{
  	color: black; 
    // color: white;
  }

   .navbar-brand {
        font-size: 1.30em;
        	transition: all 0.2s;
      }
  	#logo{
  		width: 40px;
  		height: 40px;
  			transition: all 0.2s;

  	}
  	.btn:hover{
		background-color: #2c8192;
	}
 
}



.btn-xl {
  font-weight: 700;
  font-size: 18px;
  padding: 20px 40px;
}


header.masthead{
  position:relative;
  background:url('../img/try3.jpg');
  min-height: 590px;
  background-attachment: scroll;
  background-repeat: no-repeat;
  background-position: center center;
  background-size: cover;
  text-align: center;
  color: white;

  .primary-overlay{
    background: $primary-overlay;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
  }

  
  .intro-text {
    padding-top: 300px;
    padding-bottom: 100px;
    .intro-lead-in {
      font-size: 22px;
      line-height: 22px;
      margin-bottom: 25px;
    }
    .intro-heading {
      font-size: 50px;
      font-weight: 380;
     ...

JavaScript

$(document).ready(function() {
			$(window).on("scroll", function() {
			if ($(window).scrollTop() > 100) {
			$(".navbar").addClass("compressed ");
			} else {
			$(".navbar").removeClass("compressed");
			}
			});
		
			});