custom_error_handlers.js

class ResourceNotFoundError extends Error {
  constructor(...args) {
    super(...args);
    this.trace = args[0];
    this.name = "ResourceNotFoundError";
    Error.captureStackTrace(this, ResourceNotFoundError);
  }
}

const getUser = (user_id) => {
  //if user_id exists in DB return user data
  // else throw new ResourceNotFoundError()
}

let promisifyError = fn => (...args) => fn(...args).catch(args[2])

app.get("/user/:user_id", promisifyError( async (req, res) => {
   let user = await getUser(req.params.user_id)
   return res.json(user)
}))

app.use((err, req, res, next) => {
    console.error(err.stack, err.name);
    if (err.name == "ResourceNotFoundError") {
      return res
        .status(404)
        .json({ err: err.trace.description });
    } 
    return res.status(err.statusCode || 500).json({ err: err.stack });
  });