title: How save responseText returns from GM_xmlhttpRequest?
body: <p>I tried:</p>
  
  <pre><code>GM_xmlhttpRequest({
      method: "GET",
      url: "...",
      onload: function(response) {
          r = response.responseText;
  
      }});
  alert(r); //undefined 
  </code></pre>
  
  <p>How do this?</p>