Any language in particular? For JavaScript I'd recommend https://github.com/SBoudrias/Inquirer.js

I feel the need to mention "newt" [0][1] here.

It's the C library behind whiptail, a reimplementation of dialog, which is a cli app for making menus. Incidentally, dialog is usually what you see when you get a semi-gui install with many Linux distributions.

Being C, you can use it with just about everything.

[0] https://en.wikipedia.org/wiki/Newt_%28programming_library%29

[1] https://pagure.io/newt

While not quite the same, the REPL of the Julia programming language supports modes as plugins. Out of the box there is the Julia mode for writing julia code, shell mode for shell commands and help mode for getting help on functions. But I've seen lots of interesting ways of extending this.

E.g. one of the debuggers for Julia, Gallium simply adds some new modes. So you can be in stepping-through-code-mode and then at any time switch back to Julia mode and inspect variables at that point in the execution stack.

Another mode is a package mode being developed for the new Julia package manager. So when adding, removing, updating, creating etc packages you can go into package mode and get behavior relevant to working with packages.

I had the idea of creating a mode for a board game, e.g. a Settlers of Catan mode, which is focused on issuing commands relevant to that game.

I made https://github.com/myfreeweb/interactor for Rust

I'd be interested in something like this for python

Suprised to not see ncurses mentioned anywhere yet. Not sure it's an exact match but it's well supported in the same ballpark.

Anything like this for a .NET command line application?