How to check the host correctly: Office, Office online and web browser

I need to determine if a user hit my add-in URL from a browser, outside of Office, and Office on the web. (I've seen questions here about discovery, whether it's Excel or Excel for the web, but none of them.)

I looked at the utility's functions OfficeHelpers.Utilities.host

and OfficeHelpers.Utilities.isAddin

, but the code notes say they will only work after Office. initialization is called. If the URL was migrated from outside of the Office client, this will not be the case (?).

So I think I need to do the same check as everything is done when you get a warning: Warning in Google Chrome ... to make sure Office.initialize won't run, not that it isn't already launched.

A simple use of this would be to direct users to a page that displays explanations that they cannot access it without downloading it as an add-on, along with instructions for downloading the add-on, etc.

The actual result I'm trying to get is to handle both cases as:

Inside Office client: "GetData" will return some values ​​and write them to the document. When accessed from a browser: "GetData" will return some values ​​and redirect them to the view to display them.