Is there an advantage to running code on a localhost as opposed to simply double clicking on the HTML file?

Hi Mike,

This is a good question. Let's break it down.

• Node is a server runtime for JavaScript.
• npm is the package manager for Node
• Express is a web application framework for Node that simplifies many aspects of creating a web app.
• A browser is a tool for rendering and interacting with the front end of web pages and web applications.

If your entire application is contained within a HTML file that references css and scripts that run in the user's browser, there's no need to set up the scaffolding for the serverside portions of a web application.

As your projects become more complex, you will want to do things that make a server more attractive (or other backend like AWS Lambda, API Gateway, & Dynamo DB, or Azure Functions & that stack, or the GCP stack, etc.)

Mostly, you will want certain types of application logic out of the browser and into the server. You (or your customers) will want this for a number of reasons (depending on application):

• Certain parts of the application will need to communicate with a centralised database, this will take varying amounts of time per request if this code is running in everyone's browser and being sent to a remote database - instead we will want to move this logic closer to the database to reduce the time of these requests
• In the above scenario, how does the application authenticate itself with the database? Either anyone can access any part of the database or access needs to be controlled via credentials. If all of your application is in the browser, those credentials are in the browser - this is equivalent to everyone having access.
• In a similar vein users (and competitors) should not be able to see everything the application is doing - some of it may be the source of competitive advantage or restricted by licensing terms
• Similar to the above if different user accounts are to see different things, you don't want to store all that in a place all users have access to
• Your application may need to do some heavy processing that is slow in the browser but fast on a server
• Recording stats on the way your users interact with your site require you to have somewhere to record them, and if your app works entirely in the browser it's possible to fully download it and then people can run it without a connection to your server (you won't get any stats)

The list goes on and I could probably sit here dreaming up specific cases for hours, so I'm going to leave it there and suggest you check out the MVC (Model View Controller) pattern when you get to the point where you want to start separating some of your logic out of the client.

In the mean-time, go ahead and double click that HTML file.

Cheers,

Eric