GitHub markdown TOC generator (bookmarklet)

README.md

#GitHub markdown TOC generator (bookmarklet) Drag THIS LINK to the your bookmarks

bookmarklet.js

javascript:!function(e){var r=["###Table of contents"];[].map.call(e.querySelectorAll("h1, h2, h3, h4, h5, h6"),function(e){var t=[Array(parseInt(e.tagName[1])).join("    "),"- [",e.innerText,"](",e.querySelector("a").getAttribute("href"),")"];r.push(t.join(""))}),alert(r.join("\n"))}(document.querySelector(".markdown-body"))

src.js

(function(markdownBody){
  var toc = ['###Table of contents'];
  
  [].map.call(markdownBody.querySelectorAll('h1, h2, h3, h4, h5, h6'), function(node){
    var str = [
      Array(parseInt(node.tagName[1])).join('    '),
      '- [',
      node.innerText,
      '](',
      node.querySelector('a').getAttribute('href'),
      ')'
    ];
  
    toc.push(str.join(''));
  });
  
  alert(toc.join('\n'));  
})(document.querySelector('.markdown-body'));

It didn't work for me, but the fix was easy:
On github.com, replace querySelector('a') with nextElementSibling.
On github.io, I don't know why it doesn't work. The solution is a bit different:

var str = [
      Array(parseInt(node.tagName[1])).join('    '),
      '- [',
      node.innerText,
      '](#',
      node.getAttribute('id'),
      ')'

Thanks for the bookmarklet.