JSFiddle - React, Tailwind, and code Playground

HTML

<button onclick="stopcycle()">Stop</button>

<button onclick="startcycle()">Startp</button>

JavaScript

function f1(){
  alert('f1')
}
function f2(){
  alert('f2')
}
function startcycle(){
alert('p');
var myVar=setInterval(function(){myTimer()},1000);
}
function myTimer()
{
n=1;
if(n>6){
n=1;
}
var f = 'f'+n+'()'
alert(f);
var n += 1; 
eval(f);
}

function stopcycle()
{
clearInterval(myVar);
}