somejscode.js

const currentTime = document.getElementById('timerCircle');

const currentSessionDuration = document.getElementById('sessionDuration');
const decreaseSessionTimeButton = document.getElementById('decreaseSessionTime');

function appendZeroIfNeeded(){
    let currentMinutes = parseInt(currentTime.innerText.split(':')[0]);
    if(currentMinutes<11){
        currentSessionDuration.innerText = '0'+currentSessionDuration.innerText;
    }
}


decreaseSessionTimeButton.addEventListener('click' , ()=>{
    if(currentSessionDuration.innerText>0){
        currentSessionDuration.innerText = --currentSessionDuration.innerText;
        appendZeroIfNeeded();
        currentTime.innerText = currentSessionDuration.innerText+':00';
    }
});

const increaseSessionTimeButton = document.getElementById('increaseSessionTime');
increaseSessionTimeButton.addEventListener('click' , ()=>{
    if(currentSessionDuration.innerText<60){
        currentSessionDuration.innerText = ++currentSessionDuration.innerText;
    }
});


const currentBreakDuration = document.getElementById('breakDuration');
const decreaseBreakTimeButton = document.getElementById('decreaseBreakTime');
decreaseBreakTimeButton.addEventListener('click' , ()=>{
    if(currentBreakDuration.innerText>0){
        currentBreakDuration.innerText = --currentBreakDuration.innerText;
    }
});

const increaseBreakTimeButton = document.getElementById('increaseBreakTime');
increaseBreakTimeButton.addEventListener('click' , ()=>{
    if(currentBreakDuration.innerText<60){
        currentBreakDuration.innerText = ++currentBreakDuration.innerText;
    }
});


const startTimerButton = document.getElementById('play');
function showCurrentTimeLeft(e){
    setInterval(function(){
        let currentSeconds = parseInt(currentTime.innerText.split(':')[1]);
        let currentMinutes = parseInt(currentTime.innerText.split(':')[0]);
        console.log(currentSeconds);
        if(currentSeconds==0){
            currentMinutes -= 1;
            currentTime.innerText = currentMinutes+':'+59;
        }
        else{
            let extraZeroInMinutes = '';
            let extraZeroInSeconds = '';
            if(currentMinutes<11){
                extraZeroInMinutes = '0';
            }
            if(currentSeconds<11){
                extraZeroInSeconds = '0';
            }
            currentTime.innerText = extraZeroInMinutes+currentMinutes+':'+extraZeroInSeconds+(currentSeconds-1);
        }
        if(currentSeconds == 0 && currentMinutes == 0){
            clearInterval(showCurrentTimeLeft);
        }
    },1000);
}

startTimerButton.addEventListener('click' , showCurrentTimeLeft);