title: return AJAX callback return
body: <p>For example I have a function:</p>
  
  <pre><code>var f1 = function(arg) {
      var a;
      $.ajax({
          ...
          success: function(data) {
              a = f2(data);
              //return a;
          }
      });
      //return a;
  }
  
  var f3 = function() {
      a = f1(arg);
  }
  </code></pre>
  
  <p>How can I return <code>a</code> after AJAX get <code>data</code> in <code>f1</code>?</p>