var table = new GlideTableHierarchy("task"); 
gs.info(table.getAllExtensions());

出力:わかりやすくするために改行が追加されました。

task,sc_task,problem_task,change_phase,sc_req_item,kb_submission,
release_phase,problem,ticket,sm_task,hr_task,change_task,change_request,
change_request_imac,incident,release_task,vtb_task,sm_order,hr_case,
sysapproval_group,sc_request

var table = new GlideTableHierarchy("cmdb_ci_server"); 
gs.info(table.getBase());

cmdb_ci_computer

var table = new GlideTableHierarchy("incident"); 
gs.info(table.getHierarchy());

incident,task

var table = new GlideTableHierarchy("incident"); 
gs.info(table.getName());

incident

var table = new GlideTableHierarchy("cmdb_ci_server"); 
gs.info(table.getRoot());

cmdb

var table = new GlideTableHierarchy("incident"); 
gs.info(table.getTables());

incident,task

var table = new GlideTableHierarchy("task"); 
gs.info(table.getTableExtensions());

sc_task,problem_task,change_phase,sc_req_item,kb_submission,release_phase,problem,
ticket,sm_task,hr_task,change_task,change_request,change_request_imac,incident,
release_task,vtb_task,sm_order,hr_case,sysapproval_group,sc_request

var table = new GlideTableHierarchy("incident"); 
gs.info(table.isBaseClass());

false

var table = new GlideTableHierarchy("sys_user"); 
gs.info(table.isSoloClass());

true

var table = new GlideTableHierarchy("incident"); 
gs.info(table.hasExtensions());

false