==================JavaScript function for validating userid=================

function userid_validation(uid,mx,my)
{
var uid_len = uid.value.length;
if (uid_len == 0 || uid_len >= my || uid_len < mx)
{
alert("User Id should not be empty / length be between "+mx+" to "+my);
uid.focus();
return false;
}
return true;
}

=================JavaScript function for validating password==================

function passid_validation(passid,mx,my)
{
var passid_len = passid.value.length;
if (passid_len == 0 ||passid_len >= my || passid_len < mx)
{
alert("Password should not be empty / length be between "+mx+" to "+my);
passid.focus();
return false;
}
return true;
}

=================JavaScript function for validating user name==================

function allLetter(uname)
{
var letters = /^[A-Za-z]+$/;
if(uname.value.match(letters))
{
return true;
}
else
{
alert('Username must have alphabet characters only');
uname.focus();
return false;
}
}

===============JavaScript code for validating user address===============

function alphanumeric(uadd)  {
var letters = /^[0-9a-zA-Z]+$/;
if(uadd.value.match(letters))
{
return true;
}
else
{
alert('User address must have alphanumeric characters only');
uadd.focus();
return false;
}
}

==============JavaScript code for validating ZIP code=====================

function allnumeric(uzip)
{
var numbers = /^[0-9]+$/;
if(uzip.value.match(numbers))
{
return true;
}
else
{
alert('ZIP code must have numeric characters only');
uzip.focus();
return false;
}
}

===============JavaScript code for validating email format=====================

function ValidateEmail(uemail)
{
var mailformat = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;
if(uemail.value.match(mailformat))
{
return true;
}
else
{
alert("You have entered an invalid email address!");
uemail.focus();
return false;
}
}

===============JavaScript code for validating credit card number =====================

function cardnumber(inputtxt)
{
var cardno = /^(?:3[47][0-9]{13})$/;
if(inputtxt.value.match(cardno))
{
return true;
}
else
{
alert("Not a valid Amercican Express credit card number!");
return false;
}
}

===============JavaScript code for validating phone number =====================

function phonenumber(inputtxt)
{
var phoneno = /^\d{10}$/;
if((inputtxt.value.match(phoneno))
{
return true;
}
else
{
alert("message");
return false;
}
}