JavaScript实现基于十进制的四舍五入实例

<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>