Subdomain help needed

[Chetan11-dev]

Greetings Big Commerce Developers, I am solving a problem similar to what you have solved and I thought you would may like to help.

I want to dynamically create subdomain sites such as "user1.example.com", "user2.example.com" and serve static html and css based on subdomain. For a real world example blogger.com servers html and css for different users on blogspot domain link https://althouse.blogspot.com/. I want to do exactly the same thing like blogger

Questions:

What code do I need to write for determining subdomain (using js). For example user1.example.com the subdomain is user1.
Should I store user html, css in s3 by creating folders such as user1/, user2/.
Could you tell the approach you took for your platform?