You could write the back-end in Dart, too. The Dart VM can do IO out-of-the-box. Just like the Node executable, it can be used to run command line scripts, web servers, or anything else you can think of.
Anyhow, since the front-end only communicates with the back-end via standardized protocols (say, HTTP or WebSockets), it doesn't matter what's used on the server-side. These two parts are completely decoupled.
Anyhow, since the front-end only communicates with the back-end via standardized protocols (say, HTTP or WebSockets), it doesn't matter what's used on the server-side. These two parts are completely decoupled.