JavaScript基于十进制的四舍五入实现方法

<script type="text/javascript">
  function getRoundUpOrDown(num) {
   if(isNaN(num))
     return NaN;
     // 根据对NaN进行任何进行都返回NaN的规则
   var flag = num>0 ? 1 : -1;
   return (num+flag*0.5)|0;
  }
  function logInfo(num) {
   console.log(num + ": " + getRoundUpOrDown(num));
  }
  logInfo("hell");
  logInfo("hell"+23);
  logInfo("");
  logInfo(false);
  logInfo(true);
  logInfo(2);
  logInfo(1);
  logInfo(0.7);
  logInfo(0.5);
  logInfo(0.2);
  logInfo(0);
  logInfo(-0.2);
  logInfo(-0.5);
  logInfo(-0.7);
  logInfo(-1);
  logInfo(-2);
  logInfo(9999999);
  logInfo(99999999);
  logInfo(999999999);
  logInfo(9999999999);
  logInfo(99999999999);
  logInfo(999999999999);
  logInfo(9999999999999);
  logInfo(99999999999999);
  logInfo(999999999999999);
  logInfo(9999999999999999);
  logInfo(99999999999999999);
  logInfo(00000000000000000);
</script>