GlideElement API provides different functions to work with the fields, attribute, values, etc., getDependent function on GlideElement API - helpful in validating the dependent field values if any for the given field.

Used subcategory field in incident table as an example so that it will print "category" as result. If we update the field_name variable to some other field that is not dependent on another field then the method prints null as result.

Link to documentation - https://developer.servicenow.com/dev.do#!/reference/api/paris/server_legacy/c_GlideElementAPI#r_GlideElement-getDependent