is nodejs code visible client side

JavaScript
No, Nodejs code is not visible to the client. 

To be precise Nodejs is a javascript run-time environment, 
which means it is an engine that executes javascript code. 

The server code may contain endpoints, etc, which are callable by the client, 
and which return information from the server which is rendered in the 
browser, but the client cannot see the server-side code.
Source

Also in JavaScript: