React project fails to use node modules in a git submodule - reactjs

Question

I have a Javascript (typescript) project that I am using as a git submodule in a react project (also typescript).
This all works fine... until I make use of any node module in the git submodule. I tried using, for example, the node modules "moment" and "faker", but I am almost certain that it does not have anything to do with these specific node modules.
Importing for example "moment" in the submodule:
import moment from 'moment';
using it:
moment().format('DD/MM/YYYY');
and running the main react project leads to this error:
Failed to compile.
./src/project_core/node_modules/moment/moment.js
Line 5:37: 'define' is not defined no-undef
Line 5:50: 'define' is not defined no-undef
Removing moment().format('DD/MM/YYYY'); solves it.
If I just run some tests directly in the submodule and make use of for example "moment", it always works. I can use the node modules. It looks like something goes wrong once the main project uses the node modules in the git submodule.
This is how my react project looks like. As you can see the submodule project_core is added in the src folder of the main project.
├── build
│   ├── assets
│   └── static
│   ├── css
│   └── js
├── node_modules
├── public
│   └── assets
└── src
├── project_core
│   ├── node_modules
│   ├── src
│   └── tests
├── ui
├── api
└── utils
I know... I read everywhere that using git submodules is not recommended. I, however, just want to experiment with git submodules to learn from it.

Answer 1

It looks like you have a node module inside a node module. This probably confuses your bundler and produces the import errors. Try removing the package.json and node_modules from your project core subdirectory and see if the imports work correctly. If you want to make your core directory a library think about actually having it as a npm dependency instead of a submodule. You could still reference a git commit hash in the dependency.