How to configure tsconfig.json to output files from multiple source folders to single flat outDir?

Question

I have multiple typescript projects (e.g. client and server), which share some common functionality (located in a common fold

Answer 1

As of now, you can't.

I am in a situation similar to yours, I have looked around but it seems like there is no way to change this behaviour with TypeScipt configuration.

The best you can do is use something else (a Grunt task, a shell script, ...) for moving the js files and deleting the generated folders, after every build.