Countdown timer in seconds, circular No. 50.7

The countdown timer for the site in seconds with a cyclic restart and the execution of the action at the end of the timer.

The timer counts down seconds in real time in reverse order to "0".
After the timer expires, the timer automatically restarts. Also, at the end of each timer cycle, any actions specified in the script function can be performed.

--------- Timer setting: ---------

- timer time in seconds, such as 10, 30, 60, 120 seconds, etc.
- message text.

--------- Advantages: ---------

- open source.
- without binding to the domain.
- does not depend on jQuery version.