the convention:
put the folder of the typescript module inside the src e.g in this case "day1"
mkdir src/day1
touch src/day1/index.ts
inside you could put the operation on top level, or you must put the default main function to be executed
// index.ts
export default function main() {
console.log('hello world');
}
just execute it
yarn exe day1
and, voila!