db.collection.findOne()

Optional. Controls the fields to return, or the projection. The projection argument will resemble the following prototype:

{ field1: boolean, field2: boolean ... }

The boolean can take the following include or exclude values:

• 1 or true to include. The findOne() method always includes the _id field even if the field is not explicitly stated to return in the projection parameter.
• 0 or false to exclude.

The projection cannot contain both include and exclude specifications except for the exclusion of the _id field.

Omit the projection parameter to return all the fields in the matching documents.