So lets look at an example, to see it in action
ipmo PowerShellJS Invoke-TypeScript -script "1+1"
Here we can simply load PowerShellJS then pass in an expression. Of course the above example could be lying since its valid JS as well, but its not.
There is much more to come, such as dealing with TypeScript compilation errors, doing compile only, and parsing, dealing with AMD modules and the whole enchilada.