How to create a function for custom response with Respons object in Express Js. | Node.js | Page 1

How to create a custom function for response in Express Js. I'm new to Node/express js, In Flask(Python) I can create a function (for eg: custom_response()) and return it as respone object. But when it comes to Express what I learnt is that I cannot create custom response object instead I can add properties to response objects. I'll explain it below:

const responseJSON = (res) => {
  return (status, message, data) => {
    const response = res.json({
      status: status,
      message: message,
      data: data,
    });
    return response;
  };
};

and I have created a middleware to pass attach the above function to response below:

const responseMiddleWare = (req, res, next) => {
  res.responseJSON = responseJSON(res);

  next();
};

app.use(responseMiddleWare);

so in route handler I can do like below:

router.get("/get-all-category",getAllCategory);

const getAllCategory = async (req, res) => {

  return res.responseJSON(200, "Category lists")

so here Im using res.responseJSON(), instead I'd like to know how can I return responseJSON() instead by making responseJSON() as the response object.

Is it possible in Node/Express Js?

In Express.js, the request (req) and response (res) objects are passed through the middleware stack and eventually to the route handler function, which is responsible for sending a response back to the client. As you've already learned, you can indeed attach additional properties or methods to these objects, as you're doing with res.responseJSON.

However, due to the way Express.js works, you can't exactly replace the response object itself with your own custom function or object as you can do in some other frameworks like Flask. The response object in Express is an instance of the http.ServerResponse class, and many of Express's features and middleware depend on methods and properties of this class.

The pattern you're already using, where you attach your responseJSON method to the res object in a middleware function, is actually a pretty common and idiomatic way to accomplish what you want in Express.js. It allows you to customize the format of your responses in a reusable way, without breaking the rest of Express's functionality.

If you want to simplify your route handlers further, you could wrap them in another function that automatically calls your responseJSON method. Here's a possible implementation:

const handleRoute = (handler) => {
    return async (req, res, next) => {
        try {
            const result = await handler(req, res);
            if (result !== undefined) {
                res.responseJSON(200, 'OK', result);
            }
        } catch (err) {
            next(err);
        }
    };
};

const getAllCategory = async (req, res) => {
    const categories = // ... fetch categories from database
    return categories;
};

router.get("/get-all-category", handleRoute(getAllCategory));

#How to create a function for custom response with Respons object in Express Js.