身份证js验证

<script type="text/javascript">
//--身份证号码验证-支持新的带x身份证
function isIdCardNo(num)
{
    var factorArr = new Array(7,9,10,5,8,4,2,1,6,3,7,9,10,5,8,4,2,1);
    var error;
    var varArray = new Array();
    var intValue;
    var lngProduct = 0;
    var intCheckDigit;
    var intStrLen = num.length;
    var idNumber = num;
    // initialize
    if ((intStrLen != 15) && (intStrLen != 18)) {
        //error = "输入身份证号码长度不对！";
        //alert(error);
        //frmAddUser.txtIDCard.focus();
        return false;
    }
    // check and set value
    for(i=0;i<intStrLen;i++) {
        varArray[i] = idNumber.charAt(i);
        if ((varArray[i] < '0' || varArray[i] > '9') && (i != 17)) {
            //error = "错误的身份证号码！.";
            //alert(error);
            //frmAddUser.txtIDCard.focus(); 

            return false;
        } else if (i < 17) {
            varArray[i] = varArray[i]*factorArr[i];
        }
    }
    if (intStrLen == 18) {
        //check date
        var date8 = idNumber.substring(6,14);
        if (checkDate(date8) == false) {
            //error = "身份证中日期信息不正确！.";
            //alert(error);
            return false;
        }
        // calculate the sum of the products
        for(i=0;i<17;i++) {
            lngProduct = lngProduct + varArray[i];
        }
        // calculate the check digit
        intCheckDigit = 12 - lngProduct % 11;
        switch (intCheckDigit) {
            case 10:
                intCheckDigit = 'X';
                break;
            case 11:
                intCheckDigit = 0;
                break;
            case 12:
                intCheckDigit = 1;
                break;
        }
        // check last digit
        if (varArray[17].toUpperCase() != intCheckDigit) {
            //error = "身份证效验位错误!...正确为： " + intCheckDigit + ".";
            //alert(error);
            return false;
        }
    }
    else{        //length is 15
        //check date
        var date6 = idNumber.substring(6,12);
        if (checkDate(date6) == false) {
            //alert("身份证日期信息有误！.");
            return false;
        }
    }
    //alert ("Correct.");
    return true;
}
function checkDate(date)
{
    return true;
}
function check()
{
 idnum = document.getElementById('idcard').value;
 alert(isIdCardNo(idnum));

}
</script>