facebook.js

const locale = (Array.from(document.body.classList).find(cls => cls.match(/^Locale_/)));

/**
 * Update CV tags
 * @param localeData
 */
const show_facebook_cv_tags = function(localeData) {
  const images = [...document.getElementsByTagName('img')];
  const localeRegex = new RegExp(localeData.separator_regex, 'i');

  images.forEach(el => {
    if (el.hasAttribute('data-prev-alt') &&
      el.getAttribute('data-prev-alt') === el.getAttribute('alt')) {
      return;
    }

    el.setAttribute('data-prev-alt', el.alt);

    const altText = el.alt;
    const isCVTag = altText.startsWith(localeData.tag_prefix);

    if (isCVTag) {
      const tags = altText.slice(localeData.tag_prefix.length).split(localeRegex);
      let html = '<ul class="sfcvt">';

      tags.forEach(function(tag) {
        let prefix = '∙';

        if (tag in localeData.emoji_map) {
          prefix = localeData.emoji_map[tag];
        } else if (tag.endsWith(localeData.tag_ends_with)) {
          prefix = localeData.emoji_map[localeData.tag_ends_with_map];
        }

        html += `<li>${prefix} ${tag}</li>`;
      });

      html += '</ul>';

      el.style.position = 'relative';
      el.insertAdjacentHTML('afterend', html);
    }
  });
};

/**
 * Initialize the plugin
 * @param localeData
 */
const initializePlugin = function(localeData) {
  const observer = new MutationObserver(mutations => {
    mutations.forEach(mutation => show_facebook_cv_tags(localeData));
  });

  const config = {
    attributes: true,
    childList: true,
    characterData: false
  };
  observer.observe(document.body, config);

  show_facebook_cv_tags(localeData);
};


/**
 * Make the fetch request to get locale data
 * @param localePath
 */
const makeLocaleRequest = function(localePath) {
  fetch(chrome.extension.getURL(localePath))
    .then(response => response.json())
    .then(data => initializePlugin(data))
    .catch(err => console.error('FB COMPUTER VISION TAGS ERROR', err));
};

/**
 * Check for locale
 */
if (locale === 'Locale_es_LA') {
  makeLocaleRequest('/locales/es/messages.json');
} else if (locale === 'Locale_de_DE') {
  makeLocaleRequest('/locales/de/messages.json');
} else if (locale === 'Locale_en_GB' || locale === 'Locale_en_US') {
  makeLocaleRequest('/locales/en_US/messages.json');
} else if (locale === 'Locale_fr_FR') {
  makeLocaleRequest('/locales/fr/messages.json');
} else if (locale === 'Locale_it_IT') {
  makeLocaleRequest('/locales/it_IT/messages.json');
} else if (locale === 'Locale_vi_VN') {
  makeLocaleRequest('/locales/vi_VN/messages.json');
} else if (locale === 'Locale_th_TH') {
  makeLocaleRequest('/locales/th_TH/messages.json');
}