How to stop the socket.io event on the server?

Cancel setInterval

In addition to setInterval there is a clearInterval that allows you to cancel the execution:

 const intervalId = setInterval(/*...*/); // Начинаем периодическое выполнение clearInterval(intervalId); // и останавливаем его. 

^{There are similar functions for setTimeout and setImmediate .}

Definition of user care

For each disconnection of a user, the corresponding socket creates a disconnect event. Sample code is in this answer .

Together

In the simplest case, remember the interval ID and the number of subscribing users. Change the amount when you subscribe or unsubscribe from the newsletter:

• user connection - count += 1 ;
• user exit - count -= 1 .

For each change, check:

• count 0 - make clearInterval ;
• count was 0, and became 1 - do setInterval .

 let usersSubscribed = 0; let intervalId = null; io.on('connection', function (socket) { usersSubscribed += 1; if (usersSubscribed === 1) intervalId = setInterval(/*...*/); socket.on('disconnect', function () { usersSubscribed -= 1; if (usersSubscrbied === 0) clearInterval(intervalId); }); });