JavaScript 实现随机点名系统

<!DOCTYPE html>
<html lang="en">

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

<body>
 <button id="box1">开始</button>
 <button id="box2">结束</button>
 <span id="box">Tom</span>

 <script>
  //获取页面中的元素

  var btn1 = document.getElementById('box1');
  var btn2 = document.getElementById('box2');
  var span = document.getElementById('box');
  var names = ['Tom', 'Jack', 'Lucy', 'Peter', 'Mark', 'Min', 'Liu', 'Rani'];
  var timer;

  btn1.onclick = function() {
   window.clearInterval(timer);

   timer = window.setInterval(countName, 100);
  };

  btn2.onclick = function() {
   window.clearInterval(timer);
  };

  function countName() {
   var index = parseInt(Math.random() * names.length);
   span.innerHTML = names[index];
  }
 </script>
</body>

</html>