title: How to return a value of an async function call inside a filter function
body: <p>I am trying to implement a filter to convert the month in integer format into a month string (e.g. 1 into January). The result should be translated into the selected language with angular-translate. <code>MONTH_X</code> are the identifiers in my language json file. </p>
  
  <p>The problem is, that the <code>$transclate</code> function is async and I don't know how to return a value from an async function inside a filter.</p>
  
  <p>This does not work:</p>
  
  <pre><code>app.filter('monthName', ['$translate', function($translate) {
      return function (monthNumber) { //1 = January
          var monthNames = [ 'MONTH_1', 'MONTH_2', 'MONTH_3', 'MONTH_4', 'MONTH_5', 'MONTH_6',
              'MONTH_7', 'MONTH_8', 'MONTH_9', 'MONTH_10', 'MONTH_11', 'MONTH_12' ];
  
          return $translate(monthNames[monthNumber - 1]).then(function (month) {
              return month;
          });
      }
  }]);
  </code></pre>
  
  <p>Can anybody help with this?</p>