express-rest-error

Clean error throwing/handling for Express REST apps using the Service layer pattern

Install

npm i -S express-rest-error

Example

import { validationError, errorHandler } from 'express-rest-error'
import express from 'express'

const app = express()

async function helloService(name) {
  if (!name) throw validationError('Must specify name.')
  return `Hello ${name}!`
}

app.get('/hello', async (req, res, next) => {
  try {
    const result = await helloService(req.query.name)
    res.json({ result })
  } catch (err) {
    next(err)
  }
})

app.use(errorHandler({ debug: true }))

Throwing Errors

You may throw any of the following types of errors with an optional error message.

throw validationError( message, details )

• Appropriate for missing required fields or invalid input.
• Sets the response status code to 400.

throw authRequired( message, details )

• Appropriate when token or authentication is missing.
• Sets the response status code to 401.

throw accessDenied( message, details )

• Appropriate when the user making the request does not have permission to the resource.
• Sets the response status code to 403.

throw notFound( message, details )

• Appropriate when the requested resource does not exist.
• Sets the response status code to 404.

throw customError( message, details, httpStatus )

• Appropriate for when custom errors are necessary

Handling Errors

This error handler will detect which type of error was thrown and set the status code accordingly.

Note: You should define the error handler last, after all other middleware.

app.use(errorHandler({ debug: true }))

Error Handler Options

• debug {Boolean} - (optional) returns debug output (stack trace, request data)
• transform {Function} - (optional) intercept error before sending to client

app.use(errorHandler({
  debug: true,
  transform: ({ err, req, res, responseBody }) => {
    res.setHeader('X-Warning', 'Stop sending bad requests.')
    return responseBody;
  }
}))