I have a countdown timer function here below, which counts down from 30:00. What I need is the exact same function but it counts UP from 30:00. So one second in, it should read 30:01 and so on.

Would be grateful if someone could point me in the right direction!

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

var secondsRemaining;
var intervalHandle;

function resetPage(){

    document.getElementById("inputArea").style.display = "block";

}

function tick(){
    // grab the h1
    var timeDisplay = document.getElementById("time");

    // turn the seconds into mm:ss
    var min = Math.floor(secondsRemaining / 60);
    var sec = secondsRemaining - (min * 60);

    //add a leading zero (as a string value) if seconds less than 10
    if (sec < 10) {
        sec = "0" + sec;
    }

    // concatenate with colon
    var message = min.toString() + ":" + sec;

    // now change the display
    timeDisplay.innerHTML = message;

    // stop is down to zero
    if (secondsRemaining === 0){
        clearInterval(intervalHandle);
        resetPage();
    }

    //subtract from seconds remaining
    secondsRemaining--;

}

function startCountdown(){

    function resetPage(){
        document.getElementById("inputArea").style.display = "block";
    }

    // get countents of the "minutes" text box
    var minutes = document.getElementById("minutes").value;
    
    // check if not a number
    if (isNaN(minutes)){
        alert("Please enter a number");
        return; // stops function if true
    }

    // how many seconds
    secondsRemaining = minutes * 60;
    
    //every second, call the "tick" function
    // have to make it into a variable so that you can stop the interval later!!!
    intervalHandle = setInterval(tick, 1000);

    // hide the form
    document.getElementById("inputArea").style.display = "none";


}

window.onload = function(){


        startCountdown();


    //add to the DOM, to the div called "inputArea"
    document.getElementById("inputArea").appendChild(inputMinutes);
    document.getElementById("inputArea").appendChild(startButton)       
    
document.getElementById("button").click();    

}