static-cms/packages/netlify-cms-widget-select/src/SelectPreview.js

import PropTypes from 'prop-types';
import React from 'react';
import { WidgetPreviewContainer } from 'netlify-cms-ui-default';

const SelectPreview = ({ value }) => (
  <WidgetPreviewContainer>{value ? value.toString() : null}</WidgetPreviewContainer>
);

SelectPreview.propTypes = {
  value: PropTypes.string,
};

export default SelectPreview;