React hooks displaying [Object Object] code example

Example 1: prevstate in usestate

const [prevState, setState] = React.useState([]);

setState(prevState => [...prevState, 'somedata'] );

Example 2: usestate nested object

const [currentApp, setCurrentApp] = useState({
        userID: null,
        hospitalName: null, 
        hospitalID: null,
        date: null,
        time: null,
        timestamp: null,
        slots: 1,
        appointmentType: null
    })
    
const [appointmentType, setAppointmentType] =  useState({
        Granulocytes: {
            bloodType:null,
            message: null
        }
})

const handleGranChange = (e) => {
        setAppointmentType({...appointmentType, Granulocytes : {
            ...appointmentType.Granulocytes, 
            [e.target.id] : e.target.value}
        })
		setCurrentApp({ ...currentApp, ['appointmentType'] : appointmentType  })
        console.log(currentApp)
}