Check if a file has been selected with BlueImp's JQuery File Upload

Hello, I'm using BlueImp's JQuery File Upload plugin (https://github.com/blueimp/jQuery-File-Upload) and although everything is working properly I don't know how to check if the input has a file. How can I do this?

This is my html:

<span class="btn fileinput-button">
    <i class="icon-camera"></i>
    <input id="filUserNewPostImageUpload" name="file" type="file" />
</span>

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This is the jquery:

$("#filUserNewPostImageUpload").fileupload({
   url: "/userattachment/upload/",
   dataType: "json",
   start: function(e){
      $("#hidUserNewPostAttachment").val("");
   },
   done: function (e, data) {

      if(data.result.result == "success"){
         // This returns an empty string even when a file has been uploaded successfully
         console.log($("#filUserNewPostImageUpload").val());  
      }
   }
});

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Thanks!