join in auto mode

Hi,

I am trying to implement join in auto mode. I need to join 71 messages from payload. I get an error Message missing msg.parts property-cannot join in auto mode. Can anyone please help.

var ui16 = new Int16Array(msg.payload.data); msg={payload:ui16,'parts.id':1,'parts.type':"string",'parts.count':71,'parts.ch':",",'parts.key':1,'parts.index':1}; return [msg];