count.js

var countInterval;

var current = document.querySelector('.current');
var next = document.querySelector('.next');

function startCounter(){
    var number = parseInt(document.getElementById("number").value);
    if(isNaN(number)){
        alert("Please Enter A number");
        clearInterval(countInterval);
        return;
    }
    if(number < 1 || number >  99999){
        alert("range Out of Bounds");
        clearInterval(countInterval);
        return;
    }

    var currentNos = document.querySelectorAll(".counter .current");
    var nextNos = document.querySelectorAll(".counter .next");
    var count = 0;

    resetNumbers(currentNos,nextNos,5);
    clearInterval(countInterval);

    countInterval = setInterval(function(){
        if(count==number){
            clearInterval(countInterval);
            alert("Counter has Stopped");
            return;
        }
        increaseCount(currentNos,nextNos,4);
        count++;
    },1000);
}
function resetNumbers(currentNos,nextNos,end){
    for(var i=0;i<end;i++){
        currentNos[i].innerText = 0;
        nextNos[i].innerText = 1;
    }
}

function increaseCount(currentNos,nextNos,index){
    let current = currentNos[index-1];
    let next = nextNos[index];

    if(current.innerText == 9){
        increaseCount(currentNos,nextNos,index-1);
    }
    next.classList.add("animate");
    setTimeout(function(){
        current.innerText = next.innerText;
        next.classList.remove('animate');
        next.innerText = parseInt(next.innerText) + 1;
        if(next.innerText > 9){
            next.innerText = 0;
        }
    },500);
}
// function animate(){
//     next.classList.add('animate');
    
// }