FCC - javascript certification project - markdown to html converter

markdown.js

const mdInput = document.querySelector('#markdown-input');
const htmlOutput = document.querySelector('#html-output');
const htmlPreview = document.querySelector('#preview');

const Transformers = [
  // block level elems
  [/^# (.+)/gm,  "<h1>$1</h1>"],
  [/^## (.+)/gm,  "<h2>$1</h2>"],
  [/^### (.+)/gm,  "<h3>$1</h3>"],
  [/^> (.+)/gm,  "<blockquote>$1</blockquote>"],

  // inline elems
  // bold first
  [/\*\*(.+)\*\*/gm,  "<strong>$1</strong>"],
  [/__(.+)__/gm,  "<strong>$1</strong>"],
  // italics next
  [/\*(.+)\*/gm,  "<em>$1</em>"],
  [/_(.+)_/gm,  "<em>$1</em>"],
  // img first, then a (link)
  [/!\[(.+)\]\((.+)\)/gm,  "<img alt='$1' src='$2' />"],
  [/\[(.+)\]\((.+)\)/gm,  "<a href='$2'>$1</a>"],
];


window.convertMarkdown = () => {
  return Transformers.reduce(
    (txt, [pattern, replacement]) => txt.replace(pattern, replacement),
    mdInput.value
  );
};

document.addEventListener('DOMContentLoaded', () => {
  mdInput.value = '';
  mdInput.addEventListener('input', () => {
    const txt = convertMarkdown();
    htmlOutput.textContent = txt;
    htmlPreview.innerHTML = txt;
  });
});