Minimal Mobile-friendly Off-canvas Navigation

A minimal mobile-friendly navigation that allows to reveal an off-canvas sidebar menu with a fullpage overlay when the user click on the hamburger toggle button. Built on top of pure JavaScript and CSS / CSS3. Without any dependencies like jQuery.

How to use it:

Create a menu toggle button like this:

<span id="shadowbox" onclick="menuToggle()"></span>

Create the off-canvas navigation.

<nav>
  <button id="navBtn" onclick="menuToggle()">
    <div></div>
    <div></div>
    <div></div>
    <div></div>
  </button>
  <ul id="listMenu">
    <li><a href="">Lorem</a></li>
    <li><a href="">Ipsum</a></li>
    <li><a href="">Sit</a></li>
    <li><a href="">Amet</a></li>
    <li><a href="">Sis</a></li>
    <li><a href="">Amus</a></li>
    <li><a href="">Dolor</a></li>
  </ul>
</nav>

The CSS for the menu toggle button.

span#shadowbox {
  position: absolute;
  transition: ease-in-out .5s;
}
span#shadowbox.visible {
  transition: ease-in-out .5s;
  background: rgba(0,0,0,.7);
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
}

The CSS for the off-canvas navigation.

nav {
  position: fixed;
  top: 0;
  bottom: 0;
}
nav button {
  position: relative;
  background: #99f;
  width: 48px;
  height: 48px;
  padding: 8px;
  left: 0px;
  cursor: pointer;
  transition: ease-in-out .3s;
}
nav button div {
  background: #fff;
  width: 100%;
  height: 5px;
  margin: 5px 0 0;
  float: left;
  border-radius: 9px;
  transition: ease-in-out .12s;
}
nav button div:nth-child(3) { margin: -5px 0 0 0; }
nav button div:first-child { margin: 0; }
nav button.navOpen {
  left: 250px;
  background: #f33;
  transition: ease-in-out .3s;
}
nav button.navOpen div {
  width: 100%;
  margin: 0;
  transition: ease-in-out .3s;
}
nav button.navOpen div:nth-child(1), nav button.navOpen div:nth-child(4) { background: transparent; }
nav button.navOpen div:nth-child(2) { transform: rotate(45deg); }
nav button.navOpen div:nth-child(3) {
  margin: -5px 0 0 0;
  transform: rotate(-45deg);
}
nav ul#listMenu {
  position: absolute;
  background: #3c3c3c;
  width: 250px;
  top: 0;
  bottom: 0;
  left: -250px;
  overflow: auto;
  box-shadow: 0 0 10px 0px rgba(0,0,0,0);
  transition: ease-in-out .3s;
}
nav ul#listMenu.listOpen {
  left: 0px;
  box-shadow: 0 0 10px 0px rgba(0,0,0,.5);
  transition: ease-in-out .3s;
}
nav ul#listMenu li {
  width: 100%;
  padding: 0 20px;
  float: left;
  box-sizing: border-box;
}
nav ul#listMenu li a {
  width: 100%;
  color: #fff;
  padding: 20px 10px 10px 10px;
  border-bottom: 1px solid #fff;
  float: left;
  box-sizing: border-box;
}
nav ul#listMenu li:last-child a { border: none; }

The core JavaScript to active the off-canvas navigation.

function menuToggle(){    
  if (document.getElementById("navBtn").className == "navOpen") {
    document.getElementById("navBtn").className = "";
    document.getElementById("listMenu").className = "";
    document.getElementById("shadowbox").className = "";
  } else {
    document.getElementById("navBtn").className = "navOpen";
    document.getElementById("listMenu").className = "listOpen";
    document.getElementById("shadowbox").className = "visible";
  }
}