For the Mail Merge project, I need to extract all the hyperlinks in the email message and append email tracking parameters to each of the links. The links can be either embedded in the HTML <a> tag or they can be mentioned in plain text like example.com - Gmail and other email clients are smart enough to replace such plain text website links into clickable hyperlinks.

I’m using RegEx to pull out these links from HTML / Text and then a simple JavaScript function to manipulate the link.

Replace Links inside HTML Tags

function updateLinksInHTML(html) {
  var regex = /href\s*=\s*(['"])(https?:\/\/.+?)\1/gi;
  var link;

  while ((link = regex.exec(html)) !== null) {
    html = html.replace(link[2], 'https://ctrlq.org?redirect_to' + encodeURIComponent(link[2]));
  }

  return html;
}

Convert Plain Text into Links

Some text make contain links in plain text and this method would replace such links into clickable hyperlinks by adding the anchor tag.

function createTextLinks_(text) {
  return (text || '').replace(/([^\S]|^)(((https?\:\/\/)|(www\.))(\S+))/gi, function (match, space, url) {
    var hyperlink = url;
    if (!hyperlink.match('^https?://')) {
      hyperlink = 'http://' + hyperlink;
    }
    return space + '<a href="' + hyperlink + '">' + url + '</a>';
  });
}