All Schema Types
required: boolean or function, if true adds a required validator for this property
default: Any or function, sets a default value for the path. If the value is a function, the return value of the function is used as the default.
select: boolean, specifies default projections for queries
validate: function, adds a validator function for this property
get: function, defines a custom getter for this property using Object.defineProperty().
set: function, defines a custom setter for this property using Object.defineProperty().
alias: string, mongoose >= 4.10.0 only. Defines a virtual with the given name that gets/sets this path.
immutable: boolean, defines path as immutable. Mongoose prevents you from changing immutable paths unless the parent document has isNew: true.
transform: function, Mongoose calls this function when you call Document#toJSON() function, including when you JSON.stringify() a document.