<script>
    Dropzone.options.myDropzone = {
        paramName: 'file',
        maxFilesize: 10, // MB
        maxFiles: 20,
        acceptedFiles: ".jpeg,.jpg,.png,.gif,.pdf,.doc,.docx,.xlsx,.xls",
    };

     this.on("successmultiple", function (file) {
          alert("All files have uploaded ");
      });
</script>