Bartaz/impress.js. How To Use Impress.Js. Yesterday, I wrote about Impress.js , an awesome JavaScript library for creating online presentations. Since posting online, I’ve had several people ask how exactly to use it, as there’s no set documentation on the actual project page. This guide will help you get started and allow you to create a simple slideshow, but after completing it please bear in mind that there’s so much more that can be done with it.