utils.js

var get_json = function(url, cb){
  var xmlhttp = new XMLHttpRequest()
  xmlhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      var res = JSON.parse(this.responseText)
      cb(res)}}
  xmlhttp.open("GET", url, true)
  xmlhttp.send()}

var make_element = function(tag, opts){
  opts = opts || {}
  var el = document.createElement(tag)
  if (opts["class"]) {el.setAttribute("class", opts["class"])}
  if (opts["id"]) {el.setAttribute("id", opts["id"])}
  if (opts["href"]) {el.setAttribute("href", opts["href"])}
  if (opts["text"]) {el.textContent = opts["text"]}
  return el}