Erratum NPM | npm.io

Erratum

Erratum is an extension of the native Error class that adds support for additional properties, simple assertions and can be extended as any other ES6 class.

API

new Erratum()

new Erratum([data], message)

Arguments:

data: optional additional data
message: the error message

Quick example:

const Erratum = require('erratum');
const err = new Erratum({statusCode: 500}, 'The answer is: 42');

err instanceof Error                   // true
err instanceof Erratum                 // true
err.statusCode === 500                 // true
err.message === 'This answer is: 42';  // true

Extending Erratum

Erratum can be extended as any other ES6 class.

class ExtendedErratum extends Erratum {};

const err = new ExtendedErratum({statusCode: 500}, 'The answer is: 42');
    
err instanceof Error                   // true
err instanceof Erratum                 // true
err instanceof ExtendedErratum         // true
err.statusCode === 500                 // true
err.message === 'This answer is: 42';  // true

Default values

Classes extending Erratum can specify default values to be set on their instances and optionally overridden through the data argument.

class ExtendedErratum extends Erratum {
    static get defaults() {
        return {
            ...super.defaults,
            hello: 'world',
            statusCode: 500
        }
    }
};

const err = new ExtendedErratum({statusCode: 400}, 'The answer is: 42');

err.hello === 'world'                  // true
err.statusCode === 500                 // false
err.statusCode === 400                 // true

Error wrapping

If data is an instance of Error or has either the err property or the error property set to an instance of Error, the stack of the new Erratum instance will incorporate the stack of the provided error. The latter will be available through the wrappedError property.

const err = new Error('Something went wrong.');
throw new Erratum({err}, 'Yes, something definitely went wrong.');

Erratum: Yes, something definitely went wrong.
    at repl:1:7
    at REPLServer.defaultEval (repl.js:262:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:431:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
    at REPLServer.Interface._ttyWrite (readline.js:827:14)
Caused By: Error: Something went wrong.
    at repl:1:17
    at REPLServer.defaultEval (repl.js:262:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:431:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
    at REPLServer.Interface._ttyWrite (readline.js:827:14)

Assertions

Erratum and all of its child classes support simple assertions through Erratum.assert().

Erratum.assert(check(), {statusCode: 500}, 'The answer is: 42');

Breaking changes

2.x.x
- Partial rewrite to update the code to ES6
- Dropped message formatting in favour of ES6' templates
- Dropped Erratum.extend() in favour of ES6' classes
- Dropped using the constructor as a factory function (i.e. instantiating without new)
1.x.x
- Complete rewrite, extends the native Error class to better support error specialization
- Dropped Erratum.wrap()