Problem with changing setInterval

Question

*unneccessary story*
I've made a whatsApp bot that will send a message every 30 minutes, but since I have it for a challenge with a friend I wanted to make it go every half hour - previous interval
newInterval =
1800000-previousInterval // to calc the difference
+1800000 //for an extra half hour + difference
+ Math.round(Math.random()*600000) - 300000 //random number between -5 and 5 minutes

and the interval is like this

setInterval(function(){},nieuwInterval);

How can I make the interval changing?
(btw Idc if I have to rewrite it like setInterval(send(),nieuwInterval);
function send(){}

Answer 1

if you want current interval timer run in new interval, you got to clear current interval timer first, and then set with new interval timer.

If interval changed in every timer call, better way is using setTimeout and call another new setTimeout in every timer exist.

Answer 2

Calviղ I didn't really know how but I tried this (sorry if it's completely wrong, I'm just a beginner if it is about intervals)
setInterval(function(){
...
clearInterval()
newInterval()
},x);
function newInterval(){
...
x = ...
}