Generate Table of Contents for GitHub Wiki Pages

toc.js

// How to use:
// 1. Go to a page of GitHub Wiki with Firefox.
// 2. Copy this script to the clipboard.
// 3. Hit Ctrl-Shift-K to open Web Console.
// 4. Hit Ctrl-Shift-V to paste this script.
// 5. Hit Enter to run script.
// 6. If you are not in edit mode, click the "Copy ToC" button shown in the page.
//    Then ToC is copied to the clipboard, so paste the TOC from the clipboard.

var container = document.querySelector('.markdown-body');
var isEditPage = /\/_edit$/.test(location.href.split('#')[0].split('?')[0]);
if (isEditPage) {
  let tab = document.querySelector('.preview-tab');
  tab.click();
  setTimeout(function waitPreview(retryCount) {
    container = document.querySelector('.preview-content .markdown-body');
    if (!container || (retryCount < 10 && !generateToC()))
      setTimeout(waitPreview, 250, retryCount + 1);
  }, 250, 0);
}
else {
  generateToC();
}
function generateToC() {
  var headings = container.querySelectorAll('h1, h2, h3, h4, h5, h6');
  if (headings.length == 0)
    return false;
  var minLevel = 6;
  for (let heading of headings) {
    let headingLevel = parseInt(heading.localName.charAt(1));
    if (headingLevel < minLevel)
      minLevel = headingLevel;
  }
  var toc = [];
  for (let heading of headings) {
    let anchor = heading.querySelector('a[href]');
    let href = anchor.getAttribute('href');
    let indent = '';
    let headingLevel = parseInt(heading.localName.charAt(1));
    for (let level = headingLevel - minLevel; level > 0; level--) {
      indent += '  ';
    }
    toc.push(`${indent}* [${heading.textContent.trim().replace(/\s\s+/g, ' ')}](${href})`);
  }
  var source = `<!--ToC-->
${toc.join('\n')}
 
(This ToC is generated by [ToC Generator Script](https://gist.github.com/piroor/14e42c7eeb876ab71e3202dabcd0ee9e#file-toc-js))
<!--/ToC-->`;
  if (isEditPage) {
    let tab = document.querySelector('.write-tab');
    tab.click();
    setTimeout(function updateToC(retryCount) {
      var field = document.querySelector('#gollum-editor-body');
      if (retryCount < 10 && !field.value)
        return setTimeout(updateToC, 250, retryCount);

      var matcher = /<!--ToC-->\n(.*\n)*<!--\/ToC-->/;
      if (matcher.test(field.value))
        field.value = field.value.replace(matcher, source);
      else
        field.value = `${source}

${field.value}`;
    }, 250, 0);
  }
  else {
    let button = document.createElement('button');
    button.textContent = 'Copy ToC';
    button.setAttribute('style', 'position: fixed; left: 45%; right: 45%; top: 45%;');
    button.onclick = function() {
      var textarea = document.createElement('textarea');
      document.body.appendChild(textarea);
      textarea.setAttribute('style', 'position: fixed; top: 0; left: 0;');
      textarea.value = source;
      textarea.focus();
      textarea.select();
      document.execCommand('copy');
      document.body.removeChild(textarea);
      document.body.removeChild(button);
      location.href += '/_edit';
    };
    document.body.appendChild(button);
  }
  return true;
}