(什么是[object Object] ERROR)将Dropzone.js与laravel5.5一起使用

I was following this site to use dropzone to upload multiple images with laravel5.5. But it doesn`t work.

When I upload .jpg file an error occurs. For example,

[object Object]

I want to know how to solve this. So, please give me some tips.

UploadController.php

namespace App\Http\Controllers;
use Illuminate\Http\Request;

class UploadController extends Controller
{
    public function upload(Request $request){

        $time = Carbon::now();

        $image = $request->file('file');

        $extension = $image->getClientOriginalExtension();

        $directory = date_format($time, 'Y') . '/' . date_format($time, 'm');

        $filename = str_random(5).date_format($time,'d').rand(1,9).date_format($time,'h').".".$extension;

        $upload_success = $image->storeAs($directory, $filename, 'public');

        if ($upload_success) {
            return response()->json($upload_success, 200);
        } else {
            return response()->json('error', 400);
        }
    }
}

filesystem.php

'public' => [
    'driver' => 'local',
    'root' => public_path('uploads'),
    'url' => env('APP_URL').'/uploads',
    'visibility' => 'public',
],

web.php

Route::post('/upload' , 'UploadController@upload');
Route::get('/test', function () {
return view('uptest');});

uptest.blade.php

<!doctype html><html lang="{{ app()->getLocale() }}">
    <head>
        <meta charset="utf-8">
        <script src="{{url('js/dropzone.js')}}"></script>
        <link rel="stylesheet" href="{{url('css/dropzone.css')}}">
        <title>Laravel</title>
        <script>
            Dropzone.options.myDropzone = {
                paramName: 'file',
                maxFilesize: 20, // MB
                maxFiles: 25,
                acceptedFiles: ".jpeg,.jpg,.png,.gif",

            };
        </script>   
    </head>
    <body>
        <form action="{{ url('/upload') }}" enctype="multipart/form-data" class="dropzone" id="my-dropzone">
            {{ csrf_field() }}
        </form>
    </body>
</html>

Those are which I make at localhost.