Configurable Loading Spinner With Pure JS – loadingOverlay.js
loadingOverlay.js is a standalone JavaScript library to create a configurable loading spinner (overlay) with spin handles support.
JavaScript & CSS loading overlay
Basic Loading Screen For Material Design Lite – material-loading
The material-loading lets you create a fullscreen loading screen for official Material Design Lite framework.
Minimalist Loading Overlay JavaScript Library – modalLoading
modalLoading is a minimalist JavaScript library that displays a modal-like fullscreen loading overlay / spinner for ajax requests.