检查一下：

var minutesLabel = document.getElementById("minutes");

var secondsLabel = document.getElementById("seconds");

var totalSeconds = 0;

setInterval(setTime, 1000);



function setTime() {

  ++totalSeconds;

  secondsLabel.innerHTML = pad(totalSeconds % 60);

  minutesLabel.innerHTML = pad(parseInt(totalSeconds / 60));

}



function pad(val) {

  var valString = val + "";

  if (valString.length < 2) {

    return "0" + valString;

  } else {

    return valString;

  }

}


<label id="minutes">00</label>:<label id="seconds">00</label>