.has()

Returns a boolean based on whether an element or property exists or not.

has(key)

Parameter	Description
key	String The key that will be checked

Returns	Description
Boolean	Whether or not an element or property exists in the database

db.set('prefix', '!'); // '!'

db.has('prefix'); // true

Also allows the use of dot notation:

db.set('profile', { username: '5antos' }); // { username: '5antos' }

db.has('profile.username'); // true
db.has('profile.password'); // false