title: Refused to get unsafe header "Content-Length"
body: <p>can anyone help?</p>
  
  <p>I'm newbie here</p>
  
  <pre><code>function getFileSize(url, callback) {
          var request = new XMLHttpRequest();
          //get only header.
          request.open("HEAD", url, true);
          request.onreadystatechange = function() {
              if (this.readyState == this.DONE) {
                  callback(parseInt(request.getResponseHeader("Content-Length")));
              }
          };
          request.send();
      }
  </code></pre>
  
  <p>Refused to get unsafe header "Content-Length"</p>
  
  <p>that line gives me an error >> allback(parseInt(request.getResponseHeader("Content-Length"))); in console</p>
  
  <p>can anyone help?</p>