<script>
function isDate(str)
{
    var d = new Date(str)
    return !isNaN(d)
}
</script>

function isDate(str)
{
    var reg = /^(\d{1,4})(-|\/)(\d{1,2})\2(\d{1,2})$/;
    result = str.match(reg);
    if(result == null)return false;
    var d = new Date(result[1],result[3]-1,result[4])
    var newStr = d.getFullYear()+result[2]+(d.getMonth()+1)+result[2]+d.getDate();
    return str == newStr
}

try
    {
    hdate=new Date(hyear,hmonth-1,day)
    }
catch(e)
    {
    alert('错误');
    }

<script language="JavaScript">
String.prototype.IsDate=function()
{
 var str=this;
    var reg =/^(\d+)-(\d{1,2})-(\d{1,2})$/;   
    var r=str.match(reg);   
    if(r==null)return false;   
    r[2]=r[2]-1;   
    var d=new Date(r[1],r[2],r[3]);   
    if(d.getFullYear()!=r[1])return false;   
    if(d.getMonth()!=r[2])return false;   
    if(d.getDate()!=r[3])return false;   
    return true; 
}
</script>