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        validateVatNumber = function(value) {

            var VAT_NUMBER_LENGTH = 11;

            var validVat = false;

            if(value && value.length == VAT_NUMBER_LENGTH) {

                var x = 0;
                var y = 0;

                for(var position = 0; position < VAT_NUMBER_LENGTH; ++position) {
                    if(((position + 1) % 2) > 0) {
                        x += parseInt(value.charAt(position));
                    }
                    else {
                        var double = parseInt(value.charAt(position)) * 2;

                        if(double > 9) {
                            double -= 9;
                        }

                        y += double;
                    }
                }

                if((x + y) % 10 == 0) {
                    validVat = true;
                }
            }

            return validVat;
        };