bootstrapvalidator/src/js/validator/digits.js

(function($) {
    $.fn.bootstrapValidator.validators.digits = {
        /**
         * Return true if the input value contains digits only
         *
         * @param {BootstrapValidator} validator Validate plugin instance
         * @param {jQuery} $field Field element
         * @param {Object} options
         * @returns {Boolean}
         */
        validate: function(validator, $field, options) {
            var value = $field.val();
            if (value == '') {
                return true;
            }

            return /^\d+$/.test(value);
        }
    }
}(window.jQuery));