Understanding Modules, Import and Export in JavaScript
aFarkas/lazysizes: High performance and SEO friendly lazy loader for images (responsive and normal), iframes and more, that detects any visibility changes triggered through user interaction, CSS or JavaScript without configuration.
Better lazy load for hidden pictures that will be loaded when shown, not when in viewport
Highway - A Modern Javascript Transitions Manager
Swup - complete, flexible, extensible and easy to use page transition library.
barba.js
Mavo: A new, approachable way to create Web applications
scrollnav.js
A Beginner's Guide to JavaScript's Prototype
Editor.js
formio/formio.js