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

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 isPhone(strPhone) {
	var bracket=3
	strPhone=trim(strPhone)
	if(strPhone.indexOf("+")>1) return false
	if(strPhone.indexOf("-")!=-1)bracket=bracket+1
	if(strPhone.indexOf("(")!=-1 && strPhone.indexOf("(")>bracket)return false
	var brchr=strPhone.indexOf("(")
	if(strPhone.indexOf("(")!=-1 && strPhone.charAt(brchr+2)!=")")return false
	if(strPhone.indexOf("(")==-1 && strPhone.indexOf(")")!=-1)return false
	s=stripCharsInBag(strPhone,validWorldPhoneChars);
	return (isInteger(s) && s.length >= minDigitsInIPhoneNumber);
}