how to upload and delete files from dropzone.js

For deleting thumbnails you have to enable addRemoveLinks: true, and to use "removedfile" option in dropzonejs

removedfile: Called whenever a file is removed from the list. You can listen to this and delete the file from your server if you want to.

addRemoveLinks: true,
removedfile: function(file) {
    var _ref;
    return (_ref = file.previewElement) != null ? _ref.parentNode.removeChild(file.previewElement) : void 0;
  }

I also added an ajax call for delete script and it looks like this:

addRemoveLinks: true,
removedfile: function(file) {
    var name = file.name;        
    $.ajax({
        type: 'POST',
        url: 'delete.php',
        data: "id="+name,
        dataType: 'html'
    });
var _ref;
return (_ref = file.previewElement) != null ? _ref.parentNode.removeChild(file.previewElement) : void 0;        
              }

It works on my side, so I hope it helps.