The error library contains a set of commonly used errors, and allows for easy construction of new Errors.

It will allow for instanceof checks and you don't need to use the new syntax to create an Error.

Usage

const Err = require( '@leverege/error' )

// to throw a base error, use one of these constructor types. They
// will work on any Err type.
throw Err( )
throw Err( 'My error message' )
throw Err( 'My error message', 1234 )
throw Err( 'My error message', 1234, { otherValue : 789 } )
throw Err( 'My error message', { otherValue : 789} )
throw Err( { message : 'My error message', status : 1234, otherValue : 789 } )

const e = Err()
e instanceof Err // true
e instanceof Error // true

Default Err types include


// Common Http Errors

Err.badRequest = Err.extend( 'BadRequest', 400, 'Bad arguments' )
Err.unauthorized = Err.extend( 'Unauthorized', 401, 'Unauthorized' )
Err.forbidden = Err.extend( 'Forbidden', 403, 'Forbidden' )
Err.notFound = Err.extend( 'NotFound', 404, 'Not found' )
Err.requestTimeout = Err.extend( 'RequestTimeout', 408, 'Request timeout' )
Err.conflict = Err.extend( 'Conflict', 409, 'Conflict' )
Err.gone = Err.extend( 'Gone', 410, 'Gone' )

Err.internalError = Err.extend( 'InternalError', 500, 'Internal Error' )
Err.notImplemented = Err.extend( 'NotImplemented', 501, 'Not implemented' )
Err.serviceUnavailable = Err.extend( 'ServiceUnavailable', 503, 'Service unavailable' )

// Other errors

Err.illegalArgument = Err.extend( 'IllegalArgument', 400, 'Illegal argument' ) // use BadRequest code
Err.unknownMessage = Err.extend( 'UnknownMessage', 400, 'Unknown Message' )

So, if your express request has a bad post parameter, you could do this:

app.post( '/foo' ( req, res, next ) => {
  if ( isNameInvalid( req.param.name ) ) {
    return next( Err.badRequest( 'The name is invalid') )
  }
  doStuff( next )
})

To create a new error type, use the extend() method.

Err.badStuff = Err.extend( 'BadStuff', 666, 'Bad stuff occurred' )

throw Err.badStuff()
/* will produce
{ BadStuff: Bad stuff occurred
    at Function.SubErr [as badStuff] (/Users/steve/Dev/Leverege/error/src/Err.js:50:14)
    at repl:1:5
    at ContextifyScript.Script.runInThisContext (vm.js:50:33)
    at REPLServer.defaultEval (repl.js:240:29)
    at bound (domain.js:301:14)
    at REPLServer.runBound [as eval] (domain.js:314:12)
    at REPLServer.onLine (repl.js:441:10)
    at emitOne (events.js:121:20)
    at REPLServer.emit (events.js:211:7)
    at REPLServer.Interface._onLine (readline.js:282:10) status: 666 }
*/

const bs = Err.badStuff( 'name field wasnt set' )
bs instanceof Err.badStuff // true
bs instanceof Err // true
bs instanceof Error // true
console.log( bs ) 
/*
{ BadStuff: name field wasnt set
    at Function.SubErr [as badStuff] (/Users/steve/Dev/Leverege/error/src/Err.js:50:14)
    at repl:1:10
    at ContextifyScript.Script.runInThisContext (vm.js:50:33)
    at REPLServer.defaultEval (repl.js:240:29)
    at bound (domain.js:301:14)
    at REPLServer.runBound [as eval] (domain.js:314:12)
    at REPLServer.onLine (repl.js:441:10)
    at emitOne (events.js:121:20)
    at REPLServer.emit (events.js:211:7)
    at REPLServer.Interface._onLine (readline.js:282:10) status: 666, message: 'name field wasnt set' }
*/
console.log( bs.toString() )
// BadStuff: name field wasnt set {"status":666,"message":"name field wasnt set"}