How to sum 2 columns in Interactive grid in Oracle APEX(2) using JavaScript Expression

set sal static id: sal
set comm static id:comm

create dynamic action:
event:
when sal,comm change
action:
setvalue :Javascript expression:

parseFloat($v('sal')==''? 0:$v('sal'),2)  
+ parseFloat($v('comm')==''? 0:$v('comm'),2)

affected elements: Total

• #science_technology
• #oracle_apex
• #sum_columns
• #total