Question

How I will do that:
When seconds come 31 (example 11:57 31sec.) do somthing, every minute. Using Javasript.

Thanks in advance.

Answer 1

Read the current time, calculate the number of seconds until the next time the seconds is ‘:31’ then use setTimeout with the appropriate delay. You could use something like this:

var atSeconds = 31;
var secondsLeft = atSeconds - new Date().getSeconds();
if (secondsLeft <= 0) secondsLeft += 60;
setTimeout(foo, secondsLeft * 1000);

Remember to call it again in the function foo so that it repeats.