// 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 = 5;

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);
}