i took this code from w3school where create a responsive nav bar. the nav bar add icon, add functionality for icon and change menu display. in js code, nav is assign to div element and nav has 2 case, if has class topnav or else (dont have class topnav). in html, nav has class top nav, so i dont understand what else case is for. else case is needed because when i remove else case functionality also change. please someone explain
body {
margin: 0;
font-family: Arial, Helvetica, sans-serif;
}
.topnav {
overflow: hidden;
background-color: #333;
}
.topnav a {
float: left;
display: block;
color: #f2f2f2;
text-align: center;
padding: 14px 16px;
text-decoration: none;
font-size: 17px;
}
.topnav a:hover {
background-color: #ddd;
color: black;
}
/* .topnav a.active {
background-color: #04aa6d;
color: white;
} */
.topnav .icon {
display: none;
}
@media screen and (max-width: 600px) {
/* only display home */
.topnav a:not(:first-child) {
display: none;
}
/* display icon dropdown */
.topnav a.icon {
float: right;
display: block;
}
}
@media screen and (max-width: 600px) {
.topnav.responsive {
position: relative;
}
.topnav.responsive .icon {
position: absolute;
right: 0;
top: 0;
}
.topnav.responsive a {
float: none;
display: block;
text-align: left;
}
}<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1" />
<link
rel="stylesheet"
href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css"
/>
<link rel="stylesheet" href="style.css" />
</head>
<body>
<div class="topnav" id="myTopnav">
<a href="#home">Home</a>
<a href="#news">News</a>
<a href="#contact">Contact</a>
<a href="#about">About</a>
<a href="javascript:void(0);" class="icon" onclick="myFunction()">
<i class="fa fa-bars"></i>
</a>
</div>
<script>
function myFunction() {
//objecthtmldivelement
var nav = document.getElementById("myTopnav");
// alert(nav);
if (nav.className === "topnav") {
//class responsive position icon to top right
//and display a as block text float left
nav.className += " responsive";
} else {
nav.className = "topnav";
}
}
</script>
</body>
</html>this function is for /* Toggle between adding and removing the "responsive" class to topnav when the user clicks on the icon */
else part is for removing the "responsive" class so that it remain topnav like default it was
nav.className === "topnav" is a exact match statement, so if you click the icon, the nav.className become 'topnav responsive', which is not exact match to 'topnav'(in other words, 'topnav' === 'topnav responsive' is false), this is the functionality that the else block want to handle.