> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fly.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Node.js demo reference

The Node.js demo source is on [GitHub](https://github.com/fly-apps/node-dictaphone).
`fly launch` will provide a [`Dockerfile`](https://docs.docker.com/reference/dockerfile/)
and a [`fly.toml`](/reference/configuration) config file. When you make changes to your application, you can run `npx @flydotio/dockerfile` to produce updated Dockerfiles.

How the pieces are put together:

* The original web-dictaphone app (minus the HTML) is in the
  [public](https://github.com/fly-apps/node-dictaphone/tree/main/public) directory,
  and contains icons, scripts, styles, and a web manifest; all served as
  static files.
* [`views/index.ejs`](https://github.com/fly-apps/node-dictaphone/blob/main/views/index.ejs) contains the HTML template.
* [app.js](https://github.com/fly-apps/node-dictaphone/blob/main/app.js) contains
  the server implementation, based on [Express.js](https://expressjs.com/).  There
  are lots of JavaScript frameworks out there, this is perhaps the oldest and most
  minimalist.
* The [pg](https://www.npmjs.com/package/pg) module is used to access PostgreSQL.
  Access to the database is through the `DATABASE_URL` secret.  This module is low level
  which is sufficient for this demo, but most modern Node.js applications use
  an [ORM](https://amplication.com/blog/top-6-orms-for-modern-nodejs-app-development).
* The [AWS SDK for JavaScript](https://docs.aws.amazon.com/sdk-for-javascript/v3/developer-guide/welcome.html)
  is used to access Tigris.  The following secrets are used to
  establish the connection: `AWS_ACCESS_KEY_ID`, `AWS_ENDPOINT_URL_S3`, `AWS_REGION`, `AWS_SECRET_ACCESS_KEY`, and `BUCKET_NAME`.
* The [express-ws](https://github.com/HenningM/express-ws?tab=readme-ov-file#express-ws-)
  module is used for [WebSocket](https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API) support.
* The [redis](https://github.com/redis/node-redis?tab=readme-ov-file#node-redis) module
  is used to access Redis.  The `REDIS_URL` secret is used to access the database.

Key points of logic:

* [`public/scripts/app.js`](https://github.com/fly-apps/node-dictaphone/blob/main/public/scripts/app.js)
  has been modified to make server requests at various points using
  [the Fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch).
* [`app.js`](https://github.com/fly-apps/node-dictaphone/blob/main/app.js) contains
  the logic to build responses to requests for the index page, and to GET, PUT,
  and DELETE audio clips.
* [`pubsub.js`](https://github.com/fly-apps/node-dictaphone/blob/main/pubsub.js) contains
  the logic to subscribe to a `dictaphone:timestamp` redis queue, and to
  forward updates to all open websocket connections.
* [`websocket.js`](https://github.com/fly-apps/node-dictaphone/blob/main/public/scripts/websocket.js)
  contains the client implementation of web sockets.  When update notifications
  are received, the index page is re-retrieved and the body of the DOM is
  replaced with new contents.
* When the `WHISPER_URL` secret is set, `PUT` requests will cause the audio clips
  to be passed to the Whisper server, and responses will be used to update the
  PostgreSQL database. The code for this is in [app.js](https://github.com/fly-apps/node-dictaphone/blob/1e84a4dece6888dfc68880d146b46511d47391b3/app.js#L102-L129).