title: Do synchronized XMLHTTP-requests without freezing the page
body: <p>I need to rework a website. I currently have following code:</p>
  
  <pre><code>function combinedServerRequestSync(requestParams) {
      var xmlHttp = new XMLHttpRequest();
      xmlHttp.open('POST', 'utility/php/RequestFile.php', false);
      xmlHttp.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
      xmlHttp.send(requestParams);
  
      if(xmlHttp.status === 200){
          return xmlHttp.responseText;
      } else{
          return xmlHttp.statusText;
     }
  }
  </code></pre>
  
  <p>the problem with this is, that it freezes the webpage everytime it runs. Is there a solution for this that doesn't evolve rewriting all method calls.</p>