Funny thing is I have never heard anyone say “Joisey” in my life who actually lives here. Sounds more like a Bowery boys thing. Generally people who live in North Jersey talk like people from NY and those from South Jersey like folks from Philly. Lots of people speak with generic upper middle class American accents and others speak Ebonics (albeit with a West Indian influence in certain urban areas of north Jersey).
Gov. Tom Kean used to have ads in the New York metro area, “New Juhysey and you, puhfikt togeddah.” Of course, that was a long, long time ago.