title: why xhr cannot set response type when async is false
body: <pre><code>var xhr = new XMLHttpRequest();
  
  xhr.responseType = 'json';
  
  xhr.open('GET', '/api/album/category', false);
  </code></pre>
  
  <p>//ERROR: VM829:1 Uncaught DOMException: Failed to execute 'open' on 'XMLHttpRequest': Synchronous requests from a document must not set a response type.at :1:5(anonymous function) @ VM829:1</p>
  
  <p>why xhr cannot set response type when async is false?????</p>