NPM / typescript / node.js Export functions from non module package

Question

I have 2 different projects which have some common functions.

• Project 1 : Authentication + api 1 (express but not important)
• Project 2 : Api 2 (express)

Is it possible to export Authentication function from Project 1 and use it in Project 2 ?

I tried to make a basic package but : If the Projet 1 is a module, I can't start api. If it's not, I can't import function in Project 2

Basically I want something like :

Project 1 :

• function.ts

export default function foo() {
   if (Html.isProgrammingLanguage()) return 'Boooooo';
   return 'Aha yes';
}

• index.ts

import foo from './function.ts';
// express things
router.use('/', () => {
   foo();
});

Project 2 :

• package.json

{
   "dependencies": {
      "project1": "<my git link>"
   }
}

• index.ts

import foo from 'project1';

// other express things

router.use('/', () => {
   foo();
});

Thank you in advance for your help