Handling inline images and attachments so they can be included in the merge

inlineimage.gs

// Handling inline images and attachments so they can be included in the merge
// Based on https://stackoverflow.com/a/65813881/1027723
// Get all attachments and inline image attachments
const msg = draft.getMessage();
const allInlineImages = msg.getAttachments({includeInlineImages: true, includeAttachments: false});
const attachments = msg.getAttachments({includeInlineImages: false});
const htmlBody = msg.getBody(); 
 
// Create an inline image object with the image name as key 
// (can't rely on image index as array built based on insert order)
const img_obj = allInlineImages.reduce((obj, i) => (obj[i.getName()] = i, obj) ,{});
 
// Regex to search for all img string positions with cid and alt
const imgexp = RegExp('<img.*?src="cid:(.*?)".*?alt="(.*?)"[^\>]+>', 'g');
const matches = [...htmlBody.matchAll(imgexp)];
 
// Initiate the allInlineImages object
const inlineImagesObj = {};
// built an inlineImagesObj from inline image matches
// match[1] = cid, match[2] = alt
matches.forEach(match => inlineImagesObj[match[1]] = img_obj[match[2]]);
 
GmailApp.sendEmail(recipient, subject, '', {
  name:senderName,
  from:senderEmail,
  htmlBody:htmlBody, 
  cc:allCc, 
  bcc:bcc, 
  attachments: attachments, 
  inlineImages: inlineImagesObj 
});