Express Simple Errors

Using Error Handling Middleware

import express from 'express';
import ErrorHandler, { errors } from 'express-simple-errors';

const app = express();
const errorHandler = new ErrorHandler();

app.use(errorHandler.middleware());

The middleware method will handle NotFound errors, all errors from routing, and then send the response. You can use these as one simple function, or you can use them individually.

import express from 'express';
import ErrorHandler, { errors } from 'express-simple-errors';

const app = express();
const errorHandler = new ErrorHandler();

app.use(errorHandler.handleNotFound()); //creates new NotFound() error
app.use(errorHandler.handleError()); // builds error response and stores it in res.locals.errors
app.use(errorHandler.sendResponse()); //sends error code and response

You could inject middleware after the handleError method. The original err object will be intact for you to consume before passing to sendResponse.

The stackTrace is included with the default handler method. You can turn this off when you initialize.

const errorHandler = new ErrorHandler({stackTrace: false});

Customizing the Response Object

You can modify the default handler, or create a custom one for more specific needs. The handlers are called based on the errors name property. All error classes included with this module are "Error", and the handler used will be "Default".

const defaultHandler = (err, stack) => {
  const res = {};
  res.status= err.name;
  res.message= err.message;
  res.code= err.code;
  if (stack) res.stackTrace= err.stack;
  return res;
};

Each handler will be passed two parameters - the err object, and the stackTrace flag.

To modify the Default handler, or create a custom handler, you can use the setHandler method.

errors.setHandler('Default', (err, stack) => {
  return {
    status: 'error',
    data: err.message
  }
});

errors.setHandler('Custom', (err, stack) => ('You have encountered an error.')});

Creating Error Responses

import { errors } from 'express-simple-errors';

// basic example
function foo(bar) {
  if !(bar) throw new errors.Conflict();
}

//custom message
function foo(bar) {
  if !(bar) throw new errors.Conflict('You are missing something!');
}

//used as route middleware functions
function checkUser(req, res, next) {
  try {
    const user = //do stuff to check for unser;
    if (!user) return next(new errors.NotFound('This user does not exist'));
    next();
  } catch(e) {
    next(e);
  }
}

router.route(/)
  .get(checkUser)

Supported Error Codes

• 400 BadRequest
• 401 Unauthorized
• 403 Forbidden
• 404 NotFound
• 409 Conflict
• 415 UnsupportedMediaType