Add comments to non-obvious code

app/src/api/routes/asyncController.ts

@@ -1,5 +1,12 @@
 import { Request, Response, NextFunction } from 'express';
 
+/**
+ * A wrapper for controller functions that return a Promise, enabling them to be used with Express
+ * Without this wrapper, Promise rejections caused by an error in the controller will not be passed properly
+ * to subsequent middleware layers.
+ * @param fn the async controller function to be wrapped
+ * @returns controller function which handles async errors correctly
+ */
 function asyncController(fn: (req: Request, res: Response, next: NextFunction) => Promise<any>) {
     return (req: Request, res: Response, next: NextFunction) => {
         Promise.resolve(fn(req, res, next))

app/src/helpers.ts

@@ -1,3 +1,12 @@
+/**
+ * A function to be passed to JSON.parse as a JSON reviver, in order to transform date values
+ * (which don't have a native JSON representation and therefore are serialized as strings)
+ * back to a JavaScript Date object.
+ * This works by first checking if a string value complies with a date format
+ * and then converting to a Date if and only if that's the case
+ * @param name name of the JSON field to revive
+ * @param value value of the JSON field to revive
+ */
 export function dateReviver(name, value) {
     if (typeof value === "string" && /^\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d.\d\d\dZ$/.test(value)) {
         return new Date(value);