define-error

define-error

Define errors without frills, but with stack traces and instanceof support.

example

First, create and expose a singleton that defines your errors such as errors.js:

var defineError = require('define-error')

module.exports.DatabaseError = defineError('DatabaseError')

module.exports.HttpResponseError = defineError('HttpResponseError', function (message, code) {
    this.code = code
})

Then use them:

var assert            = require('assert'),
    DatabaseError     = require('./errors').DatabaseError,
    HttpResponseError = require('./errors').HttpResponseError

function query () {
    throw new DatabaseError('No database to query silly')
}

function request () {
    throw new HttpResponseError('Nobody out there', 404)
}

try {
    query()
}
catch (err) {
    assert(err instanceof DatabaseError)
    assert(err instanceof Error)
    console.error(err)
}

try {
    request()
}
catch (err) {
    assert(err instanceof HttpResponseError)
    assert(!(err instanceof DatabaseError))
    assert(err instanceof Error)
    assert(err.code)
    console.error(err)
}

api

var defineError = require('define-error')

var CustomError = defineError('CustomError' [, initFunc])

Create an error constructor, CustomError(message). Error will be in the prototype chain. If an initFunc function is provided, it will be called in the context of the error being created with all arguments that were passed to the error constructor. This will happen after the message and stack properties are set on the error object.

install

With npm do:

npm install define-error

testing

npm test [--dot | --spec] [--phantom] [--grep=pattern]

Specifying --dot or --spec will change the output from the default TAP style. Specifying --phantom will cause the tests to run in the headless phantom browser instead of node. Specifying --grep will only run the test files that match the given pattern.

browser tests

npm run browser-tests

This will run the tests in all browsers (specified in .zuul.yml). Be sure to educate zuul first.

coverage

npm run coverage [--html]

This will output a textual coverage report. Including --html will also open an HTML coverage report in the default browser.