parcel-optimizer-ogimage/src/index.js

Set absolute URL for og:image meta tags.

// Package modules.
import { Optimizer } from '@parcel/plugin';
import url from 'url';

/*
 * Extract a meta from a given html string
 */
const findMeta = (html, propertyName, propertyValue) => {
  const regex = new RegExp(`<meta[^>]*${propertyName}=["|']${propertyValue}["|'][^>]*>`, 'i');
  const regexExec = regex.exec(html);
  if (regexExec) {
    return regexExec[0];
  }
  return false;
};

/*
 * Extract the content of a given meta html
 */
const getMetaTagContent = (metaTagHtml) => {
  const regex = /content=["]([^"]*)["]/i;
  const regexExec = regex.exec(metaTagHtml);
  if (regexExec) {
    return regexExec[1];
  }
  return false;
};

/*
 * Change the url of a meta by prepending the given baseUrl
 */
const patchMetaToAbsolute = (metaHTML, baseUrl) => {
  const metaContent = getMetaTagContent(metaHTML);
  return metaHTML.replace(
    metaContent,
    url.resolve(baseUrl, metaContent), // Relative url to absolute url
  );
};

// Exports.
export default new Optimizer({
  async optimize({

    contents,
    map,
    options,
  }) {
    const ogUrlTag = findMeta(contents, 'property', 'og:url');

    if (options.hot) {
      return { contents, map };
    }
    if (!ogUrlTag) {
      return { contents, map };
    }

    const ogUrl = getMetaTagContent(ogUrlTag);

    // Fetch original meta
    const opengraphImageMeta = findMeta(contents, 'property', 'og:image');
    if (opengraphImageMeta) {
      return {
        contents: contents.replace(
          opengraphImageMeta,
          patchMetaToAbsolute(opengraphImageMeta, ogUrl),
        ),
      };
    }
  },
});