Firestore query using an object element as parameter

Here is the answer :

.where(new firestore.FieldPath('exObject' , 'dataToQuery'), '==', "value"))

More info Here

dbRef.collection("Table").where("exObject.dataToQuery", "==", "value")

this syntax i first posted is indeed the good syntax and started working eventually. I'd class the reason of my problem as a typo that i must have corrected trying a lot of different things