The Node REPL is a useful tool for experimenting with different packages.

For example, if I wanted to see how a few of the date-fns functions worked, I could start a Node REPL session, import the package, and test them out:

$ node

const dateFns = require('date-fns')

dateFns.subDays(new Date(), 3) // returns 2021-05-28T16:03:24.476Z
dateFns.formatRelative(dateFns.subDays(new Date(), 3), new Date()) // returns 'last Friday at 12:06 PM'

As long as you have the package installed locally or globally, you can enter your Node REPL and try it out.