title: Use dart callback for wrapped js
body: <p>I wrapped exif-js library via <code>dart:js</code>.</p>
  
  <pre><code>  @JS()
      library exif;
  
      import 'package:js/js.dart';
  
      @JS()
      external PhotoDetails get EXIF;
  
      @JS()
      class PhotoDetails {
        factory PhotoDetails() {
          return EXIF;
        }
  
        @JS()
        external bool getData(img, callback);
  }
  </code></pre>
  
  <p>And have a little Dart program:</p>
  
  <pre><code>PhotoDetails photoDetails = new PhotoDetails();
      var fileUploadInputElement = new FileUploadInputElement();
      fileUploadInputElement.onChange.listen((e) =&gt; photoDetails.getData(
          fileUploadInputElement.files[0], () {
        print(this);
      }));
  </code></pre>
  
  <p><a href="https://stackoverflow.com/questions/22799289/how-do-i-create-an-anonymous-javascript-function-callback-with-darts-js-interop">Here</a> it was already answered, but when I made so, I have this js error: <code>exif.js:351 Uncaught TypeError: callback.call is not a function</code>
  I tried to cast manually to Function. But it has not helped. With lambda expression it was the same. </p>