how to determine the application exit event - applescript

Question

I created a app by script editor ,using applescript . In the code , i used "repeat ... end repeat" to mock a timer . When the code was compiled, i ran the app . it worked fine , but ,if i right click the app icon ,and chose menu "Quit" , nothing happen.
I know i should do a "EXIT" checking , but , i don't know how to do that.
Anybody can help?
on main()
set f1 to "/System/Library/Sounds/Pop.aiff"
set f2 to "/System/Library/Sounds/Ping.aiff"
set f3 to "/System/Library/Sounds/Glass.aiff"
set f4 to "/System/Library/Sounds/Tink.aiff"
repeat
set now to current date
set h to hours of now
set m to minutes of now
set s to seconds of now
if (h = 6) and (m = 30) and (s = 0) then
--some code here
end if
delay 0.5
end repeat
end main

Answer 1

The repeat loop blocks the code.
As the code is saved as application use the on idle handler which is called periodically depending on the return value.
global f1, f2, f3, f4
on run
set f1 to "/System/Library/Sounds/Pop.aiff"
set f2 to "/System/Library/Sounds/Ping.aiff"
set f3 to "/System/Library/Sounds/Glass.aiff"
set f4 to "/System/Library/Sounds/Tink.aiff"
end run
on idle
set {hours:h, minutes:m, seconds:s} to current date
if (h = 6) and (m = 30) and (s = 0) then
--some code here
end if
return 1
end idle