Does joey say "How you doing?"or "How're you doing"?

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Hi there.  In "Friends", Joey says "How you doing?" which is a shortened version of How are you doing,? meaning how are you? or how are you going?.

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Joey says,

How you doin?

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joey? a young kangaroo?

I think "How're you doing?" is the right one.  It could also be :"How do you do?" or "How are you?"

(I hope I understood your question correctly)

:)