Transformative Types

This page discusses how FirelordJS transforms your types for various uses internally.

Type transformation is needed because read(output), write(input) and compare(query) require different data types.

Conversion Table

Base	Read	Write	Compare
number	number	number | Increment	number
numeric literal	numeric literal	numeric literal	numeric literal
string	string	string	string
string literal	string literal	string literal	string literal
null	null	null	null
Timestamp | Date	Timestamp	Timestamp | Date	Timestamp | Date
ServerTimestamp	Timestamp(see point 3)	ServerTimestamp	Timestamp | Date
T[]	RecursivelyConverted<T>[]	readonly RecursivelyConverted<T>[] | ArrayUnionOrRemove<RecursivelyConverted<T>>	readonly RecursivelyConverted<T>[]
GeoPoint	GeoPoint	GeoPoint	GeoPoint
DocumentReference<M>	DocumentReference<M>	DocumentReference<M>	DocumentReference<M>
DeleteField	undefined	never for set, add and create. DeleteField for update and set merge	never
PossiblyReadAsUndefined	undefined	never	never
Record<string, T>	Record<string, RecursivelyConverted<T>>	Record<string, RecursivelyConverted<T>>	Record<string, RecursivelyConverted<T>>

FirelordJS converts base type into 3 main types for different purpose:

• Read type is the output type of getDoc, getDocs, onSnapshot and etc.
• Write type is the input type of setDoc, updateDoc, addDoc, createDoc(admin) and etc.
• Compare type is the input type for query clauses like where, orderBy, startAfter and etc.

Key Points:

1. FirelordJS forbids you from increasing numeric literal type data with increment.

2. FirelordJS forbids you from writing Date or Timestamp into ServerTimestamp, because some date time has to be server timestamp, such as createdAt and updatedAt. However if this is your intention, you can union ServerTimestamp with Date or Timestamp.

3. Firestore need time to resolve sever timestamp, so it is possible to retrieve a null value if we read the value immediately after we write it. However this is a very rare case. For smoother coding experience, I decided not to union Server Timestamp read type(Timestamp) with null anymore, users no longer need to check for null. Users can union ServerTimestamp with null in Meta Type to handle edge cases.

4. We can always compare Date or Timestamp to ServerTimestamp.

5. Timestamp(Firestore Timestamp) and Date(Javascript Date) have the same transformation, use either one as base type.