function myFn() {console.log('idle');}
var myTimer = setInterval(myFn, 4000);
// Then, later at some future time,
// to restart a new 4 second interval starting at this exact moment in time
clearInterval(myTimer);
myTimer = setInterval(myFn, 4000);
var myVar = setInterval(myTimer, 1000);
function myTimer()
{
var d = new Date();
var t = d.toLocaleTimeString();
document.getElementById("demo").innerHTML = t;
}
function myStopFunction()
{
clearInterval(myVar); // stops interval
}