Morphing Hamburger Navigation Using JavaScript And CSS Clip-path

A mobile-friendly hamburger navigation that morphs the hamburger button into a fullscreen menu using JavaScript and CSS transition, transform and clip-path properties.

How to use it:

Create the hamburger navigation.

<nav class="nav">
  <ul>
    <li>Home</li>
    <li>Contact</li>
    <li>About</li>
    <li>Blog</li>
  </ul>
</nav>

Create a hamburger button to toggle the navigation.

<button class="nav-tgl" type="button" aria-label="toggle menu">
  <span aria-hidden="true"></span>
</button>

The necessary CSS/CSS3 rules for the navigation & hamburger button.

.nav-tgl {
  display: inline-block;
  cursor: pointer;
  position: fixed;
  z-index: 100;
  right: 30px;
  top: 30px;
  width: 70px;
  height: 70px;
  border: none;
  border-radius: 50%;
  padding: 0;
  background: #fff;
  box-shadow: 0px 4px 24px rgba(0, 0, 0, 0.24);
  line-height: 0.6;
  text-align: center;
}
.nav-tgl > span {
  display: inline-block;
  position: relative;
  height: 2px;
  width: 34px;
  border-radius: 1px;
  background: #293335;
  vertical-align: middle;
}
.nav-tgl > span:before, .nav-tgl > span:after {
  display: inline-block;
  position: absolute;
  content: "";
  height: 2px;
  border-radius: 1px;
  background: #293335;
  transition: all 200ms;
}
.nav-tgl > span:before {
  top: -11px;
  left: 3px;
  width: 28px;
}
.nav-tgl > span:after {
  top: 11px;
  left: 6px;
  width: 22px;
}
.nav-tgl:focus {
  outline: none;
}
.nav-tgl:hover > span:after, .nav-tgl:hover > span:before {
  width: 34px;
  left: 0;
}
.nav-tgl.toggled > span {
  height: 0;
}
.nav-tgl.toggled > span:after, .nav-tgl.toggled > span:before {
  top: 0px;
  left: 0;
  width: 34px;
}
.nav-tgl.toggled > span:after {
  transform: rotate(-45deg);
}
.nav-tgl.toggled > span:before {
  transform: rotate(45deg);
}
.nav:before {
  display: block;
  position: fixed;
  top: 0;
  left: 0;
  content: '';
  width: 100vw;
  height: 100vh;
  background: rgba(0, 0, 0, 0.8);
  transition: all 500ms ease-in-out;
  clip-path: circle(30px at calc(100% - 65px) 65px);
  visibility: hidden;
}
.active.nav:before {
  visibility: visible;
  clip-path: circle(100%);
}
.nav ul {
  display: none;
}

The main JavaScript to enable the hamburger navigation.

let toggled = false;
const nav = document.getElementsByClassName('nav')[0];
const btn = document.getElementsByClassName('nav-tgl')[0];
btn.onclick = function(evt) {
  if (!toggled) {
    toggled = true;
    evt.target.classList.add('toggled');
    nav.classList.add('active');
  } else {
    toggled = false;
    evt.target.classList.remove('toggled');
    nav.classList.remove('active');
  }
}