title: onreadystatechange is not called in firefox
body: <p>Here are my codes.</p>
  
  <p>my function to send ajax request and return a value:</p>
  
  <pre><code>function myAjaxCall(){
     var myValue=0
     var async= false //I have to use synchronized request(otherwise my return value is 0)
     xmlhttp.open("GET",URL,async);
  
     xmlhttp.onreadystatechange=function(){
         ...
         myValue = SOMEVALUE;
     };
  
     xmlhttp.send();         
  
     return myValue
  }
  </code></pre>
  
  <p>My other function will use the myAjaxCall function returned value</p>
  
  <pre><code>function otherFunc(){
     var x= myAjaxCall();
  }
  </code></pre>
  
  <p>Things are working perfectly in this way except on <strong>Firefox</strong> browser, I know the reason is because in Firefox, if I use <strong>synchronized</strong> request, the <code>onreadystatechange</code> will not be called. </p>
  
  <p>In my case, however, I have to use <strong>synchronized</strong> ajax request, otherwise <code>myAjaxCall()</code> function returned value is always the initail value "<code>var myValue=0</code>".</p>
  
  <p>How to get rid of this firefox problem??</p>