npm i async-jsonstore-io in your preferred terminal / command prompt or just install it from the repl.it packages tab.
Include it in your app using
const JsonStoreClient = require('async-jsonstore-io')
Here's a link to the github repository. ( It will be greatly appreciated if you star it too. )
Official npmjs.com page ( also contains the docs for more help )
Also make sure to check out jsonstore.io to see what it is if you don't already know.