JavaScript获取某年某月的最后一天

1、实现源码
<!DOCTYPE html>
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<html>
    <head>
        <title>JavaScript获取某年某月的最后一天</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width">
        <script type="text/javascript">
              /**
               * 获取某年某月的最后一天
               */
              function getLastDayOfMonth(year,month)
              {
                  //获取本年本月的第一天日期
                  var date = new Date(year,month-1,'01');
                  //设置日期
                  date.setDate(1);
                  //设置月份
                  date.setMonth(date.getMonth() + 1);
                  //获取本月的最后一天
                  cdate = new Date(date.getTime() - 1000*60*60*24);
                  //打印某年某月的最后一天
                  alert(cdate.getFullYear()+"年"+(Number(cdate.getMonth())+1)+"月最后一天的日期:"+cdate.getDate()+"日"); 
                  //返回结果
                  return cdate.getDate();
              }
        </script>
    </head>
    <body>
        <input type="button" value="获取某年某月的最后一天" οnclick="getLastDayOfMonth(2014,6)"/>
    </body>
</html>
2、实现结果