Index generator for GFM (Github Formated Markdown) documents. Just run it in the JS console.

makeIndex.js

function makeIndex(){
  var indexDiv = document.createElement("div");
  var a = document.getElementsByClassName("anchor");
  var i, log="";
  for (i=0; i<a.length;i++){
    var aa = document.createElement("a");
    aa.href="#"+a[i].name;
    aa.innerHTML=a[i].parentElement.innerText;
    indexDiv.appendChild(aa);
    indexDiv.appendChild(document.createElement("br"));
    log += '- ['+aa.innerHTML+']('+"#"+a[i].name+')\n';
  }
  
  // Markdown list to paste in document
  console.log(log);
  
  // Insert above the first paragraph (for preview)
  document.getElementsByTagName("p")[0].insertBefore(indexDiv, document.getElementsByTagName("p")[0].firstChild);
}