code: function getAndCache (url) {
    var xhr = new XMLHttpRequest(); // eslint-disable-line
  
    if (cache[url]) {
      return cache[url]
    }
  
    xhr.open('GET', url, false);
    xhr.send();
    var script = xhr.responseText;
    cache[url] = evalJS(script);
    return cache[url]
  }
docs: Simple ajax get
  @param {string} url
  @return { then(resolve, reject), abort }