js_progress/calculator.html at master · Max-hearted/js_progress · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>

  <style>
    input{
      font-size: 20px;
      font-weight: bold;
      text-align: right;

    }
  </style>
</head>
<body>

  Minutes:<input type="text" value="0"><br/>
  Seconds:<input type="text" value="0"><br/>
  <button type="button">开始计时</button>

<script type="text/javascript">

  var minuteNode = document.getElementsByTagName('input')[0];
  var secondNode = document.getElementsByTagName('input')[1];
  var btn = document.getElementsByTagName('button')[0];


  btn.addEventListener('click', function() {

    var minute = 0;
    var second = 0;
    var timer = setInterval(function() {
      second ++;
      if(second == 60) {
        second = 0;
        minute ++;
      }
      secondNode.value = second;
      minuteNode.value = minute;

      if(minute == 3) {
        clearInterval(timer);
      }
    },10);
  });


</script>

</body>
</html>