JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdn.steemjs.com/lib/latest/steem.min.js"></script>

<pre id="counter"></pre>

JavaScript

(function() {

  // call the main function
  whoUpvotedMe('pilcrow').then(result => {
    // print the results in the HTML
    document.getElementById('counter').innerText = JSON.stringify(result, null, 4);
  });

  function whoUpvotedMe(username) {
    return steem.api.getDiscussionsByAuthorBeforeDate(username, null, '2100-01-01T00:00:00', 100)
      .then(posts => {
          const allUpvoters = getAllUpvoters(posts);
          return countUpvoters(allUpvoters);
      });
  }
    
  function getUpvoters(post) {
      return post.active_votes.map(upvote => upvote.voter);
  }
  
  function getAllUpvoters(posts) {
    return posts.reduce((all, currentPost) => {
        const upvoters = getUpvoters(currentPost)
        return all.concat(upvoters);
    }, []);
	}
  
  function countUpvoters(allUpvoters) {
   return allUpvoters.reduce((upvoteCounts, upvoter) => {
  upvoteCounts[upvoter] = (upvoteCounts[upvoter] || 0) + 1;
        return upvoteCounts;
    }, {});
	}
})();