function dragLeaveHandler(event) {

         console.log("drag leave");

        // Set style of drop zone to default

         event.target.classList.remove('draggedOver'); 

      }

      function dragEnterHandler(event) {

        console.log("Drag enter");

        // Show some visual feedback

        event.target.classList.add('draggedOver'); 

      }

       function dragOverHandler(event) {

         //console.log("Drag over a droppable zone");

         // Do not propagate the event

         event.stopPropagation();

         // Prevent default behavior, in particular when we drop images or links

          event.preventDefault(); 

      }

      function dropHandler(event) {

          console.log('drop event');

         // Do not propagate the event

         event.stopPropagation();

         // Prevent default behavior, in particular when we drop images or links

          event.preventDefault(); 

        // reset the visual look of the drop zone to default

        event.target.classList.remove('draggedOver'); 

        // get the files from the clipboard

        var files = event.dataTransfer.files;

        var filesLen = files.length; 

        var filenames = "";

        // iterate on the files, get details using the file API

        // Display file names in a list.

    for(var i = 0 ; i < filesLen ; i++) {

        filenames += '\n' + files[i].name; 

        // Create a li, set its value to a file name, add it to the ol

        var li =     document.createElement('li');

        li.textContent = files[i].name;    document.querySelector("#droppedFiles").appendChild(li);

    }

     console.log(files.length + ' file(s) have been dropped:\n' + filenames);

         uploadAllFilesUsingAjax(files);

      }  

      function uploadAllFilesUsingAjax(files) {

         var xhr = new XMLHttpRequest();

         xhr.open('POST', 'upload.html');

        xhr.upload.onprogress = function(e) {

            progress.value = e.loaded;

            progress.max = e.total;

        };

        xhr.onload = function() {

            alert('Upload complete!');

        };

        var form = new FormData();

        for(var i = 0 ; i < files.length ; i++) {  

           form.append('file', files[i]);

        }

        xhr.send(form);

      }