Getting the to be rendered filename extension with Extendscript

Is there a way to get the file extension in extend script that the outputModule will render a composition as?

I found the line below in the docs, but the format isn't exactly what I need and I haven't been able to find much more by using the docs.  It doens't have to be from the outputModule, but that's the closest I've come to finding something.

var current_format = app.project.renderQueue.item(1).outputModule(1).getSettings(GetSettingsFormat.STRING).Format;

For a use case example, a user can use my extension to render a composition that is then uploaded to storage. I can build the path up until the file name extension (.mp4, .avi, etc.), but I haven't figured out a way to build the final part of the path like I can in Premiere. 

var current_format = app.project.renderQueue.item(1).outputModule(1).getSettings(GetSettingsFormat.STRING).Format;

And in case I didn't explain that well, here's what I'm hoping to do:

var rqItem = app.project.renderQueue.items.add(comp);
var fileExtension = rqItem.outputModule(1).getFileExtension() (ex. returns ".mp4")
var outputPath = "/path/to/file/" + rqItem.name + fileExtension
rqItem.outputModule(1).file = new File(outputPath)

The ES docs that I referenced before: https://ae-scripting.docsforadobe.dev/renderqueue/outputmodule.html#outputmodule-getsettings