@conjurelabs/err

Errors

Extending native errors, to give a little more context.

This is useful for differentiating between server (5xx) and user (4xx) errors. As well as making sure internal vs. public-facing error messages are different.

Install

npm install --save @conjurelabs/err

Usage

const { ConjureError } = require('@conjurelabs/err')

throw new ConjureError('something happened')

Public-Facing Errors

Internal error dialogs may not be appropriate for end users. Default 'public' errors are set on every Conjure error.

const { NotFoundError } = require('@conjurelabs/err')

const err = new NotFoundError('sensitive message')

console.log(err.message) // 'sensitive message'

console.log(err.publicMessage) // 'A needed resource was not found'

This can be used to pass back non-sensitive errors to the client, while still logging actual error messages internally.

// in a final express route handler
server.use((err, req, res, next) => {
  if (!err) {
    return next()
  }

  console.log(err) // will log true error message & stack trace

  if (err instanceof ConjureError) {
    return res.status(err.httpStatusCode).send({ message: err.publicMessage })
  }

  // if a native (non ConjureError), then 500
  res.status(500).send({ message: 'An error occurred '})
})

You can signal that a set error message is okay for public users, by passing public: true in an options argument.

const err = new NotFoundError('The file you have requested is not present', { public: true })

This will set .publicMessage to 'The file you have requested is not present'

HTTP Status Codes

Similar to 'public' errors, you may also want to know what http status code an error should associate to.

const { PermissionsError } = require('@conjurelabs/err')

const err = new PermissionsError(`User doesn't have access`)

console.log(err.httpStatusCode) // 403

Wrapping a Native Error

If you want to extend a native error, you can pass in the entire err instance.

const { PermissionsError } = require('@conjurelabs/err')

try {
  await checkPermissions()
} catch(err) {
  throw new PermissionsError(err)
}

Tests

npm test
npm run lint