We pass hashid as an identifier of the habit and calendar templates.

hashids are generated using 'hashids' module.

We create an encryption key for the hashing. eg.
    var hashids = new Hashids('This is my salt');

And then we pass the encrypted hashid to the UI
    hashids.encodeHex(result.document._id);

When an habit or calendar item is marked, we decrypt the hashid to get the original id.
Then update the item as marked or unmarked.
    hashids.decodeHex(req.body.hashid);