// Declaring required variables
var digits = "0123456789";
// non-digit characters which are allowed in phone numbers
var phoneNumberDelimiters = "()- ";
// characters which are allowed in international phone numbers
// (a leading + is OK)
var validWorldPhoneChars = phoneNumberDelimiters + "+";
// Minimum no of digits in an international phone no.
var minDigitsInIPhoneNumber = 10;

function isInteger(s)
{   var i;
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character is number.
        var c = s.charAt(i);
        if (((c < "0") || (c > "9"))) return false;
    }
    // All characters are numbers.
    return true;
}

function stripCharsInBag(s, bag)
{   var i;
    var returnString = "";
    // Search through string's characters one by one.
    // If character is not in bag, append to returnString.
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character isn't whitespace.
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}

function checkInternationalPhone(strPhone){
	s=stripCharsInBag(strPhone,validWorldPhoneChars);
	return (isInteger(s) && s.length >= minDigitsInIPhoneNumber);
}
 
function echeck(str) {
	var at="@"
	var dot="."
	var lat=str.indexOf(at)
	var lstr=str.length
	var ldot=str.indexOf(dot)
	if (str.indexOf(at)==-1){
	   alert("Invalid email address")
	   return false
	}
	if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
	   alert("Invalid email address")
	   return false
	}
	if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
	    alert("Invalid email address")
	    return false
	}
	 if (str.indexOf(at,(lat+1))!=-1){
	    alert("Invalid email address")
	    return false
	 }
	 if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
	    alert("Invalid email address")
	    return false
	 }
	 if (str.indexOf(dot,(lat+2))==-1){
	    alert("Invalid email address")
	    return false
	 }	
	 if (str.indexOf(" ")!=-1){
	    alert("Invalid email address")
	    return false
	 }
	 return true					
}

function checkRegistrationForm()
{
	with (window.document.frmRegistration) {
		if (isEmpty(txtUsername, 'Enter user name')) {
			return false;
		} else if (isEmpty(txtPassword, 'Enter password')){
			txtPassword.focus();
			return false;
		} else if (isEmpty(txtFirstname, 'Enter your first name')){
			txtFirstname.focus();
			return false;
		} else if (isEmpty(txtLastname, 'Enter your last name')){
			txtPassword.focus();
			return false;
		} else if (isEmpty(txtPhone, 'Please Enter your Phone Number')) {
			txtPhone.focus();
			return false;
		} else if (checkInternationalPhone(txtPhone.value)==false){
			alert("Please Enter a Valid Phone Number");
			txtPhone.value="";
			txtPhone.focus();
			return false;
		} else if (isEmpty(txtEmail, 'Enter an email address')){
			txtEmail.focus();
			return false;
		} else if (echeck(txtEmail.value)==false){
			txtEmail.value="";
			txtEmail.focus();
			return false;
		} else {
			submit();
		}
	}
}