Как сохранить таймер в localstorage и возобновить его при перезагрузке страницы?

let timerInterval;
let timerStart;
let time = 0;
 
function updateTime() {
  time++;
  let mins = parseInt(time / 60);
  let secs = time % 60;
  if(mins < 10) {
    mins = '0' + String(mins);
  }
  if(secs < 10) {
    secs = '0' + String(secs);
}
document.querySelector('#timespan').innerHTML = `${mins}:${secs}`;  
} 
 
function startTimer() {
  timerInterval = setInterval(updateTime, 1000);
  time = 0;
  timerStart = true;
};
 
function stopTimer() {
  clearInterval(timerInterval);
  time = 0;
  timerStart = false;
}
 
document.querySelector('.save-btn').addEventListener('click', () => {
  localStorage.setItem('currentTime', document.querySelector('#timespan').innerHTML);
}
 
window.addEventListener('load', () => {
  document.querySelector('#timespan').innerHTML = localStorage.getItem('currentTime');
}, false );

let timerInterval;
let time = 0;
 
function updateTime() {
  time++;
  let mins = parseInt(time / 60);
  let secs = time % 60;
  if(mins < 10) {
    mins = '0' + String(mins);
  }
  if(secs < 10) {
    secs = '0' + String(secs);
}
document.querySelector('#timespan').innerHTML = `${mins}:${secs}`;
}
 
function startTimer() {
  timerInterval = setInterval(updateTime, 1000);
};
 
function stopTimer() {
  clearInterval(timerInterval);
}
 
document.querySelector('.save-btn').addEventListener('click', () => {
  localStorage.setItem('currentTime', time);
});
 
window.addEventListener('load', () => {
  time = parseInt(localStorage.getItem('currentTime'));
  if(isNaN(time)) time = 0
  startTimer()
}, false );