"Attribute metatype" is the Type-R attribute type descriptor with metadata attached. Metatype is created by assigning the result of type( T ) expression to some variable.

The following attribute types are available from @type-r/ext-types package.

Date attribute represented in JSON as Microsoft date (represented in JSON as string /Date(timestamp))

Date attribute represented in JSON as UNIX timestamp (the result of date.getTime()).

Number attribute converting value to integer on assignment. Can be called as function.

String attribute with email validation check.

String attribute with IP address validation check.

String attribute with URL validation check.