两道面试题

1.还是上次的求 2 的 1000000 次方的后五位的（脑子挖塌了）根本就没必要算出来所有的位数，乘法只要后5位就行了呗...............

var num = 2,
        str = null; 
    for (var i = 1; i < 1000000; i++) {
      num *= num;
      str = num.toString();
      if(str.length > 5) {
        str = str.slice(-5);
      }
      num = +str;
    }
    console.log(num);

2.制作一个获取本地事件的钟表　　　　这里主要就是用到了 css3 的 transform rotate()

<!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>
    html,body{
      height: 100%;
    }
    .box{
      width: 400px;
      height: 400px;
      background: pink;
      border-radius: 50%;
      position: relative;

      transform: rotate(-90deg)
    }
    .shi{
      width: 100px;
      height: 20px;
      background: yellow;
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translateY(-10px);
      z-index: 3;
      transform-origin: left;

    }
    .fen{
      width: 150px;
      height: 18px;
      background: magenta;
      position: absolute;
      left: 50%;
      top: 50%;
      transform: translateY(-7.5px);
      z-index: 2;
      transform-origin: left;
      
    }
    .miao{
      width: 200px;
      height: 10px;
      background: green;
      position: absolute;
      left: 50%;
      top: 50%;
      transform: translateY(-5px);
      z-index: 1;
      transform-origin: left;
      
    }
    .start{
      width: 100px;
      height: 50px;
      background: #000;
      color: #fff;
      font-weight: 700;
      text-align: center;
      line-height: 50px;
    }
    .start:hover{
      cursor: pointer;
    }
  </style>
</head>
<body>



  <div class="box">
    <div class="shi"></div>
    <div class="fen"></div>
    <div class="miao"></div>
  </div>


  <div class="start" onclick="new Run()">启动</div>
  <script>
    

    function Run () {
      this.getDom();      
      this.first();
    }
    Run.prototype.first = function() {
      var now = new Date(),
          shi = null,
          fen = null,
          miao = null,
          timer = null;
      
      shi = now.getHours();
      fen = now.getMinutes();
      miao = now.getSeconds();
      console.log(shi + '-----' + fen + '-----' + miao );

      
      miao = miao * 6;
      fen = fen * 6;
      shi = shi * 30;

      console.log(shi + '-----' + fen + '-----' + miao );

      console.log(oHours);
      
      oHours.style.transform = 'rotate('+ shi + 'deg)';
      oSeconds.style.transform = 'rotate('+ miao + 'deg)';
      oMinutes.style.transform = 'rotate('+ fen +'deg)';      
      timer = setInterval(function(){
        miao += 6;
        fen += 6/60;
        shi += 6/60/60;
        oHours.style.transform = 'rotate('+ shi + 'deg)';
        oSeconds.style.transform = 'rotate('+ miao + 'deg)';
        oMinutes.style.transform = 'rotate('+ fen +'deg)';
      },1000)
      
      //点击一次绑定一个清除定时器的事件
      oBtn.addEventListener('click',goon);
      function goon() {
        clearInterval(timer);
        oBtn.removeEventListener('click',goon);
      }
      
    }
    Run.prototype.getDom = function() {
      oHours = document.getElementsByClassName('shi')[0];
      oMinutes = document.getElementsByClassName('fen')[0];
      oSeconds = document.getElementsByClassName('miao')[0];
      oBtn = document.getElementsByClassName('start')[0];
    }

     

  
  </script>
</body>
</html>

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原文地址：https://www.cnblogs.com/96weibin/p/8625327.html