Backend ​

What is the backend? ​

Our backend webserver is what we use for the frontend to communicate to our database and to other clients. For example, we might want to store a new message and push it to all connected users within 100 meters of its sender. These are operations that neither the front end nor the database can do by themselves, so we need a server as our middleman.

As we already write our frontend in TypeScript, we've opted to use it in our backend along with Node.js, for consistency's sake. Node.js is a JavaScript runtime; that is, we can run a JavaScript server on our computers (whereas traditionally, the language could only be used in a web browser). The TypeScript code compiles into JavaScript, making this possible.

Our database ​

For our database, we've elected to use Firebase's Cloud Firestore, which is developed by Google. The reasons why we're using this vary from cost to simplicity while working with Node. Firebase also has a variety of other services we may use if we finish our MVP and release our app to the public.

A clear description of many function parameters can be found in the Firestore Reference.

Express.js ​

Express.js is the framework we use for our REST API, handling HTTP requests sent from clients. More on this in the REST API section.

Directory structure ​

This explanation pertains to everything inside of server/src in our codebase.

index.ts ​

This is the entry point to the server, or the first file invoked when the server runs. It contains code that decides what to do when an HTTP request is received and manages client WebSocket connections.

/actions ​

This directory contains code for speaking directly to the database. We segment most things into files with create, get, update, and delete operations, following the CRUD acronym. The main reason for this segmentation is for readability purposes (we don't want an index file with thousands of lines of code for you to search through).

/types ​

This directory contains files that hold type information, working with a feature of TypeScript. These types correlate to how we store documents and collections in our database. Using these types throughout our code helps us catch errors when a certain attribute isn't being accounted for, or if one is being implemented incorrectly.

/utilities ​

This directory contains files that perform functionality related to operating the server itself. For example, connecting to Firestore.