window.onload = function () {
  var index = document.getElementById("index");
  var headers = document.getElementsByTagName("h1");
	
  for (var i = 0; i < headers.length; i++)
  {
    var headerId = "index" + i;
    headers[i].id = headerId;

    var liElement = document.createElement("li");
    var aElement = document.createElement("a");
    aElement.setAttribute("href", "#" + headerId);
    aElement.innerHTML = headers[i].innerHTML;
    liElement.appendChild(aElement);
    index.appendChild(liElement);
  }
}