You can use Express as a static file server for a HTML website or SPA.
Using the Notificaitons API, you can send system-level notifications to a user.
Express provides a simple sytnax for creating a REST API in Node.js.
You can use Promise.all or Promise.allSettled to wait for multiple requests to complete.
How to emails to one or more addresses and including attachments.
Multer allows files and any additional form data to be easily parsed from a request.
Learn how for both an input the 'multiple' attribute and with multiple input elements.
First get the data in blob or blob-like format and then access its size property.
You can combine lastIndexOf() and slice() to get the file extension.