append to array mongoose updateone
/*Another way to push items into array using Mongoose is-
$addToSet, if you want only unique items to be pushed into
array. $push operator simply adds the object to array whether
or not the object is already present, while $addToSet does that
only if the object is not present in the array so as not to
incorporate duplicacy.*/
PersonModel.update(
{ _id: person._id },
{ $addToSet: { friends: friend } }
);