External module without import statement in Typescript

Question

The moment you add an import statement to your Typescript file, this file is considered an external module. So this is not a problem:

File.1.ts

import { Type } from '...';
let whatever = 123;
...

File.2.ts

import { Type } from '...';
let whatever = 234;
...

So this works. But the moment one removes those two import statements, these files aren't considered modules any more and both variables with the same name become global interfering with each other.

Question

How does one force modularization of a source file that doesn't have any import statements?

Answer 1

It is required to import or export something. I suggest to export an undefined value:

export let undefined;

The compiler generates no code for this instruction.