textbox value should not be more than 14 character and take only integer value

//textbox onblur Event

asp:TextBox ID="TextBox1" runat="server" onblur="Checktextboxlenth(this);">/asp:TextBox>



//.js file

function ValidateCCNum(ccNum)
{
var ccno = ccNum.value;
if(ccno == "")
{

return true;
}

if(isNaN(ccno))
{

alert("Credit card number should be numeric");
ccNum.value="";
ccNum.focus();

return false;
}


if(ccno.length < 14 || ccno.length >18)
{

alert("Credit card number should have 14-18 digits length");
ccNum.value="";
ccNum.focus();

return false;
}
return true;
}