delete a document from firestore code example
Example: firestore javascript delete document
// define document location (Collection Name > Document Name > Collection Name >)
var docRef = Firebase.firestore().collection("Rooms").doc("bsYNIwEkjP237Ela6fUp").collection("Messages");
// delete the document
docRef.doc("lKjNIwEkjP537Ela6fhJ").delete();