I'm currently writing my code in TypeScript, and I'm not using a library like Webpack to bundle the code. I've set the declaration flag to true in my tsconfig.json to ask TypeScript to generate declarations for the code. I'm making a class accessible on the window object for external scripts to make use of, and I'm currently doing so with the following code (Foo.ts):

(() => {
    class Foo {
        // ...
    }

    (window as any).Foo = Foo;
})();

When transpiled into JavaScript, this works and the Foo class can be found on the window object. However, the declaration file (Foo.d.ts) contains nothing.

I assumed that this was because the file wasn't exporting anything, so I changed the code to export the variable (and place it in the top-level rather than in a closure) and it worked. However, specific to my use case, it made no sense to "export" a variable when the script is going to be loaded in the browser (of course, unless I used something like Webpack).

This is so far preventing me referencing the class type in integration tests. I can't simply declare the variable for use either since it would require writing my own d.ts file (which defeats the purpose of just using TypeScript) nor can I declare it midway through my existing Foo.ts file since TypeScript does not allow non-top-level declares. It wouldn't make sense for me to add in Webpack to the toolchain and add more bloat to a small script that doesn't use any dependencies either.

I've actually run into this same issue trying to get types for oojs-ui, which does the same thing. Unfortunately, I'm not as keen to simply set window.Foo to any in my tests and hope for the best.

How can I have TypeScript emit the declaration for the Foo class, without needing an export statement? In other words, how can I have TypeScript export declarations for a class appended to the window variable?