In order to customize the error response , you need to create a class which extend class ErrorHandler and override the available methods.

e.g - Let's say you want to customize the error response for status code - 404.

import { ErrorHandler } from "fortjs";

export class CustomErrorHandler extends ErrorHandler {
    async onNotFound(url){
       return  htmlResult(`<h1>The resource ${url} does not exist.</h1>`);
    }
}

So basically it returns a customized http response similar to worker.

Now you have created the class, you need to inform fortjs about this.

import { Fort } from "fortjs";
import { UserController } from "./controllers";
import { CustomErrorHandler } from "./extra/custom_error_handler";


//add routes
Fort.routes = [{
    controller: UserController,
    path: "/user"
}];

Fort.errorHandler = CustomErrorHandler;    

Fort.create();

The methods available for override are -

• onServerError(ex: IException): Promise
• onBadRequest(ex: IException): Promise
• onForbiddenRequest(): Promise
• onNotAcceptableRequest(): Promise
• onMethodNotAllowed(): Promise
• onNotFound(url: string): Promise

You can see some methods also have parameters. So its upto you how you want to use those params.

e.g - for onServerError (Status code - 500), you should not show the exception information to users but you should definitely log those errors.

Note:- It is highly recommended to create a custom error handler and atleast override the onServerError method and log the exception, otherwise you won't have any information regarding the exception occured.