JavaScript实现背景颜色实时动态变化

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    #dv {width: 100px;height: 100px;}
  </style>
</head>
<script>
  window.onload=function(){
    var oDv = document.getElementById('dv');
      oDv.style.backgroundColor='red'
    setInterval(function(){
      var arrRandNumber = [
          getRandomNumber(0,255),
          getRandomNumber(0,255),
          getRandomNumber(0,255)   
        ];
 
      oDv.style.backgroundColor='rgb('+arrRandNumber[0]+','+arrRandNumber[1]+','+arrRandNumber[2]+')'
         
        function getRandomNumber(rMin,rMax){
          var cha = rMax-rMin;
          var rand = Math.random();
          //return (rMin+Math.round(cha*rand))
        }
       
    },500)
     
    //alert(getRandomNumber(0,255))
  };
</script>
<body>
  <div id="dv"></div>
</body>
</html>