Popper.js is a library used to create poppers in web applications.So what is a popper? A popper is an element on the screen which “pops out” from the natural flow of your application.
Common examples of poppers are tooltips and popovers.
Popper.js is mostly a library with the job of making sure your popper stays near the defined reference element (if you want so).
Additionally, it provides an easy way to generate your popper element if you don’t want to use one already in your DOM.
Popper.js is just ~3.5KB minified and gzpipped, no dependencies required!