Can anyone explain why this pattern doesn't work? Or point me to some resource?

  function myApiFunc(callback)
  {
    /*
     * This pattern does NOT work!
     */
    try {
      doSomeAsynchronousOperation(function (err) {
        if (err)
          throw (err);
        /* continue as normal */
      });
    } catch (ex) {
      callback(ex);
    }
  }