javascript - 如何在javascript中计算两个日期时间之间的天数？

Question

如何计算两个日期时间之间的天数？
请参阅下面我的代码:

<script type="text/javascript">
    // how to count days between two date time ?
    var a= '2014-03-21 12:00:12';
    var b = '2014-05-11 18:00:00';
    function days_diff(a,b){
        // .....
        // ..... placeholder ....
        // ..... placeholder ....
        // ..... placeholder ....
        // ..... placeholder ....
        // ..... placeholder ....
        // .....
        // var days = days_a - days_b;
        return days;
    }

</script>   

Answer 1

  <script>
    var oneDay = 24*60*60*1000; // hours*minutes*seconds*milliseconds
    var firstDate = new Date(2008,01,12);
    var secondDate = new Date(2008,01,22);
    var diffDays = Math.round(Math.abs((firstDate.getTime()-secondDate.getTime())/(oneDay)));
  </script>