If these are supposed to represent constant values, then please remove them from the attachment instance's own properties. The code in this file should instead be wrapped in an IIFE:

```js


(function(exports) {
  'use strict';
  
  var MIN_THUMBNAIL_WIDTH_HEIGHT = 80;  // min =  80px
  var MAX_THUMBNAIL_WIDTH_HEIGHT = 120; // max = 120px
  var MAX_THUMBNAIL_GENERATION_SIZE = 400 * 1024; // 400 KB


  << existing code here >>

  exports.Attachment = Attachment;

}(this));

```