Countdown timer in JavaScript

Just to piggy back off this. I use a different method that uses variables instead of off-canvas text boxes and allows for MM:SS or HH:MM:SS formatting. I've attached an example.

The X_minute_duration variable value is the number of seconds in the time you want it to count down, the X_minute_duration_display is how it will be seen by users and the X_minute_finished one is what you can use to trigger other things once it changes. For different times, you just need to set the variable values correctly and if you rename them, update the code. 

These work really well, I've got about 20 on a single slide in one project that all run independently and trigger as they should - including duplicate ones that use the same variables but are triggered at different times.