text: let hr = (min = sec = ms = "0" + 0);
  let startTimer;
  
  const startBtn = document.querySelector(".start");
  const stopBtn = document.querySelector(".stop");
  const resetBtn = document.querySelector(".reset");
  
  startBtn.addEventListener("click", start);
  stopBtn.addEventListener("click", stop);
  resetBtn.addEventListener("click", reset);
  
  function start() {
    startBtn.classList.add("active");
    stopBtn.classList.remove("stopActive");
  
    startTimer = setInterval(() => {
      ms++;
      ms = ms < 10 ? "0" + ms : ms;
  
      if (ms == 100) {
        sec++;
        sec = sec < 10 ? "0" + sec : sec;
        ms = "0" + 0;
      }
      if (sec == 60) {
        min++;
        min = min < 10 ? "0" + min : min;
        sec = "0" + 0;
      }
      if (min == 60) {
        hr++;
        hr = hr < 10 ? "0" + hr : hr;
        min = "0" + 0;
      }
      putValue();
    }, 10);
  }
  
  function stop() {
    startBtn.classList.remove("active");
    stopBtn.classList.add("stopActive");
  
    clearInterval(startTimer);
  }
  
  function reset() {
    startBtn.classList.remove("active");
    stopBtn.classList.remove("stopActive");
  
    clearInterval(startTimer);
    let hr = (min = sec = ms = "0" + 0);
    putValue();
  }
  
  function putValue() {
    document.querySelector(".millisecond").innerText = ms;
    document.querySelector(".second").innerText = sec;
    document.querySelector(".minute").innerText = min;
    document.querySelector(".hour").innerText = hr;
  }
  