Answers for "javascript function do something every 30 seconds"

javascript run every 5 seconds

const interval = setInterval(function() {
   // method to be executed;
 }, 5000);

clearInterval(interval); // thanks @Luca D'Amico

js every x seconds

// your function
function myTimer() {
    console.log(' each 1 second...');
}

var myVar = setInterval(myTimer, 1000); //setting the loop with time interval

clearInterval(myVar); //call this line to stop the loop