A quick loading overlay to be used when switching views or during heavy procssing.

Overlay.js

// To use as your page loading:
// Best way is to embed in your HTML a DIV.overlay, without the hidden class
// This way, your page is loaded with the overlay on
// Do your initialization stuff, then just stop the loading, voilà!

// Attach to window to make it globally available in your runtime
window.overlay = document.querySelector('#overlay');

// ... Or, built an overlay DOM element when required
window.overlay = document.createElement('DIV');
window.overlay.className = 'overlay hidden';
document.body.appendChild(window.overlay);

// Use this line to start the loading and add the overlay
requestAnimationFrame(() => window.overlay.classList.remove('hidden'));

// Use this one to stop the loading and remove the overlay
requestAnimationFrame(() => window.overlay.classList.remove('hidden'));

Overlay.scss

@keyframes rotate {
  0% {
    transform: perspective(120px) rotateX(0deg) rotateY(0deg);
  } 50% {
    transform: perspective(120px) rotateX(-180.1deg) rotateY(0deg);
  } 100% {
    transform: perspective(120px) rotateX(-180deg) rotateY(-179.9deg);
  }
}

.overlay {
  background-color: rgba(0, 0, 0, .7);
  height: 100%;
  left: 0;
  position: absolute;
  top: 0;
  width: 100%;
  z-index: 9999;
  
  &.hidden {
    display: none;
  }

  &::before {
    content: '';
    background-color: rgb(55, 195, 64);
    border-radius: 5px;
    height: 50px;
    left: calc(50% - 25px);
    position: absolute;
    top: 50%;
    width: 50px;

    animation: rotatePlane 1.2s infinite ease-in-out;
  }
}