How to check Office AddIn Host is running an Outlook application using office.js?

Using the Office.js Api how do you determine the current App being used "Office.context.requirements.isSetSupported" only seems to work for Excel & Word, and I would like to check for Outlook.

You can use different URLs for the add-in between excel/word and outlook. Or you can check Office.context.mailbox - if it's defined, then you're running in Outlook.