@eriksturesson/backend-error v0.0.3

Backend-error

Simple logging

Installation

npm install @eriksturesson/backend-error

🔥 Custom BackendError class

Use BackendError class for standardized backend error handling:

Usage

import { BackendError } from "@eriksturesson/backend-error";

throw BackendError.BadRequest("Missing required field");

Or construct it manually for full control:

const error = new BackendError({
  message: "Something went terribly wrong",
  severity: "critical",
  showUser: true,
  code: 500,
  data: { context: "PaymentService", id: 12345 },
});

Properties available:

• message: The error message
• code: HTTP status code
• isOperational: Marks it as a handled error (vs. crash)
• showUser: Whether frontend should show the message
• severity: "info" | "warning" | "error" | "critical"
• data: Additional metadata (optional and anything accepted)

You can extend it for custom domains too.

🧠 Example: With Express + showUser handling

import { BackendError } from "@eriksturesson/backend-error";

app.get("/user/:id", async (req, res, next) => {
  try {
    const user = null;
    if (!user) throw BackendError.NotFound("User not found");
    res.json(user);
  } catch (err) {
    if (err instanceof BackendError && err.showUser) {
      res.status(err.code ?? 400).json({ error: err.message });
    } else {
      res.status(500).json({ error: "Internal Server Error" });
    }
    next(err);
  }
});

Available static error constructors

• BackendError.BadRequest(message: string) // 400, showUser: true
• BackendError.Unauthorized(message: string) // 401, showUser: true
• BackendError.Forbidden(message: string) // 403, showUser: true
• BackendError.NotFound(message: string) // 404, showUser: true
• BackendError.Conflict(message: string) // 409, showUser: true
• BackendError.UnprocessableEntity(message: string)// 422, showUser: true
• BackendError.Internal(message: string) // 500, showUser: false
• BackendError.ServiceUnavailable(message: string) // 503, showUser: false

🧩 httpErrorFormatter(error) – Format backend errors for HTTP responses

This helper takes an Error (or BackendError) and returns a plain object with:

✅ status – an HTTP status code (number)

✅ body – a JSON.stringify'd string representing the error (already parsed)

It’s designed to be simple and universal – you can use it with any framework (Azure Functions, Express, etc).

🔧 Example usage

import { BackendError, httpErrorFormatter } from "@eriksturesson/backend-error";

try {
  throw BackendError.Internal("Something went very wrong."); // 👈 your static factory pattern
} catch (err) {
  const { status, body } = await httpErrorFormatter(err);

  return {
    status,
    headers: {
      ...getCorsHeaders(request.headers.get("origin")), // Add CORS headers yourself
    },
    body,
  };
}

⚠️ Important This function does not include any HTTP headers – especially no CORS headers. Why? Because every environment has different CORS rules.

If you're using Azure Functions, Express, or something else, you'll need to add CORS manually:

🧩 Types

export type Severity = "info" | "warning" | "error" | "critical";

export interface BackendErrorOptions {
  message: string;
  isOperational?: boolean;
  showUser?: boolean;
  severity?: Severity;
  code?: number;
  data?: any;
}

🌐 Repo

https://github.com/eriksturesson/backendError

Created by @eriksturesson