Error handling in large uploads to Express using Formidable and AJAX

[MatthewCole-PDX]

I have created a private server and web application for uploading movies and playing them. Unfortunately, uploads often interupt and fail. The console log shows the upload is to be terminated, but progress continues until the end where it reaches 100%, but never completes. I would like it to either stop the upload in the event of a network interruption, or better yet, gracefully catch the error and continue such that the upload completes correctly. I am using formidable, a nodejs library in an express framework with Ajax on the front end to display a progress bar. Here is my code:

app.post('/upload', (req, res) => {

// create an incoming form object
  var form = new formidable.IncomingForm();

  form.maxFileSize = 2500 * 1024 * 1024;
  form.multiples = true;

  form.uploadDir = path.join(__dirname, '/public/dropbox/');

  form.on('file', function(field, file) {
     fs.rename(file.path, path.join(form.uploadDir, file.name), () => {
         console.log(file.name + " uploaded")
     });
  });

  form.on('progress', (bytesReceived, bytesExpected) => {
  });

  process.on('uncaughtException', function(err) {  //this does nothing
     console.log(err)
     throw err;
  })

  form.on('error', function(err) {
     console.log('An error has occured: \n' + err);
     res.eventEmitter('error')
  });

  // once all the files have been uploaded, send a response to the client
  form.on('end', function() {
     console.log("finished uploading")
  });

  // parse the incoming request containing the form data
form.parse(req);
})

And on the front end in AJAX:

$('#upload-input').on('change', function(){
   $("#error").css("display", "none");
   var files = $(this).get(0).files;
   console.log(files[0].name);
   if (files.length > 0){
      // create a FormData object which will be sent as the data payload in the
     // AJAX request
     var formData = new FormData();
     // loop through all the selected files and add them to the formData object
     for (var i = 0; i < files.length; i++) {
        var file = files[i];
        // add the files to formData object for the data payload
        formData.append('uploads[]', file, file.name);
     }
     $.ajax({
         url:''/upload',
         type: 'POST',
         data: formData,
         processData: false,
         contentType: false,
         success: function(data){
            console.log('upload successful!\n');
             window.location.href = window.location.pathname;
             $('').html(data)
         },
         error: function(data, status, error){
             console.log(data, status, error)
             //this does nothing
         },
         xhr: function() {
             // create an XMLHttpRequest
             var xhr = new XMLHttpRequest();
             // listen to the 'progress' event
             $('.progress').show();
                xhr.upload.addEventListener('progress', function(evt) {
                   if (evt.lengthComputable) {
                      // calculate the percentage of upload completed
                      var percentComplete = evt.loaded / evt.total;
                      percentComplete = parseInt(percentComplete * 100);
                      // update the Bootstrap progress bar with the new percentage
                      $('.progress-bar').text(percentComplete + '%');
                      $('.progress-bar').width(percentComplete + '%');
                      // once the upload reaches 100%, set the progress bar text to done
                      if (percentComplete === 100) {
                          $('.progress-bar').html('Done');
                      }
                   }
                }, false);
                xhr.upload.addEventListener('error', function(err) {
                    xhr.abort()
                    $("#error").css("display", "block");
                })
                return xhr;
             }
          });