Response to preflight request doesn't pass?

I have an React App which fetch api(the code below) from a backend Server which is in Laravel(PHP).

export const createVenue = (venueData) => dispatch => {
    console.log('action called');
           fetch('http://localhost:8001/api/venues', {
                   method: 'POST',
                   headers: {
                        'Accept': 'application/json',
                       'Content-Type': 'application/json'
                       },
                   body: JSON.stringify({
                       venueData
                   })
               })
               .then(res=>res.json())
               .then(venue=>
            dispatch({
                type: NEW_VENUE,
                payload: venue
            })
            );
};

And I have set a Middleware with routes on server to accept CORS request as below:

class Cors {

    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {

        return $next($request)
        ->header('Access-Control-Allow-Origin','*')
        ->header('Access-Control-Allow-Methods','GET, POST, PUT, DELETE, OPTIONS')
         ->header('Access-Control-Allow-Headers', 'Content-Type');
    }

}

Here are the routes:

Route::group(['prefix' => 'api/','middleware' => 'cors'], function() {

    Route::get('venues',[
    'as' => 'apiVenueGet',
    'uses' => 'Api\Venue@index'
    ]);
    Route::post('venues',[
    'as' => 'apiVenuePost',
    'uses' => 'Api\Venue@create'
    ]);

});

But when i am using to submit form I am getting this in console of browser:

Failed to load http://localhost:8001/api/venues: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

Now the problem can get solved if I Use following header in my fetch call:

headers: {
                        'Accept': 'text/plain',
                       'Content-Type': 'application/json'
                       },

or with x-form-urlencode,

can anybody explain why application/json doesnt work here?

via Chebli Mohamed