Http Api Errors

This is a simple package that provides strongly typed http errors that extends the Error class with a status code

Install

npm i http-api-errors

Usage

import { BadRequest, expressJsonCatchHandler } from "http-status-errors";
import express from "express";

const app = express();

app.get("/", () => {
  if(inputIsInvalid) throw new BadRequest("Input is invalid")
})

app.use(expressJsonCatchHandler());

// You can also use a logger
const logger = { warn: console.warn }; // you only need warn

app.use(expressJsonCatchHandler({ logger }))

Aysnc usage

import handler from "express-async-handler";
import { NotFound, expressJsonCatchHandler } from "http-api-errors";

app.get("/user/:id", handler(async (req, res) => {
  const user = await getUser(req.params.id);
  if(user == null) throw new NotFound(`User with id ${req.params.id} not found`);
}))

JSON Catch Handler

The expressJsonCatchHandler will catch an error in the request chain and respond with a json formatted error in this form (example)

// 404 Not Found
{
  "error": {
    "status": 404, // number
    "message": "User not found" // string
  }
}

The status code will default to err.status or 500

If the error has a Symbol.for("http-api-errors.error.toHttpError") the conversion will be made

And if the error has a Symbol.for("http-api-errors.error.isDisplayable") the message will be sent to the user, otherwide Internal error will be sent as the message

Extending

Errors such as NotFound, BadRequest, etc. extends the HttpError class and are displayable by default

Other errors can be converted to an HttpError with the property [Symbol.for("http-api-errors.error.toHttpError")] that must be a function that returns an HttpError:

Errors can be marked as displayable by setting to true the property [Symbol.for("http-api-errors.error.isDisplayable)] Displayable errors will sent to the user with their message, not displayable errors will default to the message Internal error

If your error has the status property, it will be used as the status code of the response

import { HttpError, Internal, kToHttpError, kIsDisplayable } from 
import assert from "assert";

assert.equal(kToHttpError, Symbol.for("http-api-errors.error.toHttpError"));
assert.equal(kIsDisplayable, Symbol.for("http-api-errors.error.isDisplayable"));

// custom errors
export class MyAwesomeError extends HttpError {
  
  // you can add any props you want with any names and types
  metadata: Metadata;

  constructor(status: number, message: string, metadata: Metadata) {
    super(status, message);
    this.metadata = metadata;
  }


  // If you wanna to expose extra data to the client of your api
  // you should override the toJSON() method
  toJSON() {
    return {
      status: this.status,
      messsage: this.message,
      metadata: this.metadata,
    }
  }
}

// covertible errors
export class ConvertibleError extends Error {
  [kToHttpError]() {
    return new Internal("Some user-facing message here");
  }
}

// displayable errors
export class DisplayableError extends Error {
  
  stauts: number;
  [kIsDisplayable]: boolean;

  constructor(status, message) {
    super(message);
    this.status = status;
    this[kIsDisplayable]: true;
  }
}

Convert

You can convert any catched type to an HttpError

status will default to err?.status or 500

message will default to err?.[kIsDisplayable] ? String(err?.message) : "Internal error"

import { toHttpError } from "http-api-errors";

try {
  someFunctionThatMayFail()
} catch(err) {
  httpError = toHttpError(e);
}