Extract and Replace Links in HTML with JavaScript RegEx

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Published in: JavaScript - Regular Expressions

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.

function updateLinksInHTML(html) {

  var regex = /href\s*=\s*(['"])(https?:\/\/.+?)\1/ig;
  var link;

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

  return html;

}

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>';
    }
  );
};
Published in: JavaScript - Regular Expressions

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Web Geek, Google Developer Expert
A
Amit Agarwal

Amit Agarwal is a Google Developer Expert in Google Workspace and Google Apps Script. He holds an engineering degree in Computer Science (I.I.T.) and is the first professional blogger in India. He is the developer of Mail Merge for Gmail and Document Studio. Read more on Lifehacker and YourStory

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