Detect "Desktop Mode" on mobile devices

[psavva]

Is your feature request related to a problem? Please describe.
I want to understand if my application is running on a mobile device, but in 'Desktop Mode'

Describe the solution you'd like
I would like a new flag (true/false) isDesktopMode, that will tell me if the browser is running on a mobile device running in desktop mode.

Describe alternatives you've considered
I could implement a check on my software, but think it would be better for the community if we are able to have this here.

Additional context
Mobile devices have limited resources and just due to it running in desktop mode, it doesn't mean it has the resource of it. As a developer, I would like to know what device it really is.