gist-to-bookmarklet-html.js

'use strict';

const rows = Array.prototype.slice.apply(
  document.querySelectorAll('.js-file-line')
);

const code = rows
  .map(el =>
    el.innerHTML
      .replace(/<[^>]*>/g, '')
      .replace(/&lt;/g, '<')
      .replace(/&gt;/g, '>')
      .replace(/&amp;/g, '&')
      .replace(/%0A/g, '\n')
  )
  .join('\n')
;

const lnk = document.createElement('a');
lnk.href = `data:text/html;base64,${btoa(code)}`;
lnk.textContent = document.title;
lnk.setAttribute('class', 'btn btn-sm');

document.querySelector('.file-actions').appendChild(lnk);