To prevent the main div from shifting to the right, you can achieve this by specifying
style.marginLeft = "0px"
within the openNav() function.
function openNav() {
document.getElementById("mySidebar").style.width = "250px";
document.getElementById("main").style.marginLeft = "0px";
}
function closeNav() {
document.getElementById("mySidebar").style.width = "0";
document.getElementById("main").style.marginLeft= "0";
}
body {
font-family: "Lato", sans-serif;
}
.sidebar {
height: 100%;
width: 0;
position: fixed;
z-index: 1;
top: 0;
left: 0;
background-color: #111;
overflow-x: hidden;
transition: 0.5s;
padding-top: 60px;
}
.sidebar a {
padding: 8px 8px 8px 32px;
text-decoration: none;
font-size: 25px;
color: #818181;
display: block;
transition: 0.3s;
}
.sidebar a:hover {
color: #f1f1f1;
}
.sidebar .closebtn {
position: absolute;
top: 0;
right: 25px;
font-size: 36px;
margin-left: 50px;
}
.openbtn {
font-size: 20px;
cursor: pointer;
background-color: #111;
color: white;
padding: 10px 15px;
border: none;
}
.openbtn:hover {
background-color: #444;
}
#main {
transition: margin-left .5s;
padding: 16px;
}
/* On smaller screens, where height is less than 450px, change the style of the sidenav (less padding and a smaller font size) */
@media screen and (max-height: 450px) {
.sidebar {padding-top: 15px;}
.sidebar a {font-size: 18px;}
}
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body>
<div id="mySidebar" class="sidebar">
<a href="javascript:void(0)" class="closebtn" onclick="closeNav()">×</a>
<a href="#">About</a>
<a href="#">Services</a>
<a href="#">Clients</a>
<a href="#">Contact</a>
</div>
<div id="main">
<button class="openbtn" onclick="openNav()">☰ Open Sidebar</button>
<h2>Collapsed Sidebar</h2>
<p>Click on the hamburger menu/bar icon to open the sidebar, and push this content to the right.</p>
</div>
</body>
</html>