how to update element of an array of objects nested in an object?

How can I update an array of objects nested inside an object? I am trying to create this object using the useState hook.

This is my code:

	const [hotelForm, setHotelForm] = useState({
		HotelLocation: "",
		CheckInOn: "",
		CheckOutOn: "",
		
		 rooms: [
		 	{
		 		roomNo: 1,
		 		noOfPersons: 2,
		 		ageOfPerson1: 0,
		 		ageOfPerson2: 0,
		 		
		 	},
		 ],
		 rooms: props.rooms,
	});

Here, I am trying to update the value of the rooms array when the form input field value changes. In the same rooms array, other room objects (objects made using roomNo, noOfPersons, etc.) can be added.

How can I update this array of objects using state? If possible, I would also like to know how to do it using vanilla JavaScript, not React.

This would be a good case for using a reducer (https://react.dev/reference/react/useReducer) which helps to deal with complex states and/or different state updates.

Also, changing the data structure of the rooms to a map makes it easier to read/write data from/to your state and you don't have to iterate over all of your room every time.

const reducer = (state, action) => {
   const {type, roomId, ...roomData} = action;
   switch(type) {
     case 'updateRoom': return {
        ...state,
        rooms: {
           ...state.rooms,
           [roomId]: {
             ...state.rooms[roomId],
             ...roomData
           }
        }
     }
   }
};

const defaultState = {
  HotelLocation: "",
  CheckInOn: "",
  CheckOutOn: "",
  rooms: {
     1: {
        noOfPersons: 2,
        ageOfPerson1: 0,
        ageOfPerson2: 0,
     }
  }
}

const [state, dispatch] = useReducer(reducer, defaultState);

Later, if you need to update sth. you can call sth like this:

dispatch({type: 'updateRoom', roomId: 1, ageOfPerson1: 20});

You can add more cases to your reducer function depending on your needs. e.g. adding a new room, removing one, etc.

This code is not fail-safe, you'll need to add some error handling.
Here You can find some more examples of reducers & complex states.