Is There A Way To Prevent Duplication Of Entries In NeDB Collection's Array?

var addNewUser = function (id, chatId) { db.update({ _id: id }, { $push: { users: chatId } }, {}, function (err, numAffected) { // code after the record is updated

Solution 1:

To push new chatId to users array only if it does not exist, you can use $addToSet. According to the nedb document:

$addToSet adds an element to an array only if it isn't already in it

Here is the example code:

var addNewUser = function (id, chatId) {
  db.update({ _id: id }, { $addToSet: { users: chatId } }, {}, function (err, numAffected) {
    // code after the record is updated
  });
}