eventuate

eventuate

Handle events without emitters. If we had to do it all over again, we might do it this way...

example

var eventuate = require('eventuate'),
    assert    = require('assert')

// create an event type, let us call it request
// kind of like an EventEmitter for a single event type
var request = eventuate()

// consume all requests (think .on)
function onRequest (req) {
    // do something
}
request(onRequest)

// make sure someone is listening
assert(request.hasConsumer)

// produce an event
request.produce({ url: '/test' })

// remove our consumer
request.removeConsumer(onRequest)

See example/compare.js for more compare/contrast between eventuate and EventEmitter.

api

var eventuate = require('eventuate')

var event = eventuate(options)

Create an object, event, that represents a consumable event type.

Valid options are:

• requireConsumption - throw an error if a produced event is not consumed, useful for error producers
• monitorConsumers - [default: true] true or false, see "unmonitored eventuate" below

event(consumer)

Consume events with the consumer function, which should have the signature function (data) {}. When an event is produced, it will be passed to the consumer function as the first and only argument.

event.forEach(consumer)

Alias for event(consumer) as described above.

event.produce(data)

Produce an event. All event consumer functions will be called with data. If the requireConsumption option was provided, and nothing consumes the data, an error will be thrown. In this case, if the data being produced is an instanceof Error, it will be thrown directly, otherwise an UnconsumedEventError (see below) will be thrown, and the data that was produced will be attached to the error as a data property.

event.removeConsumer(consumer)

Remove the formerly added consumer, so that it will not be called with future produced events.

event.removeAllConsumers()

Remove all consumers from the eventuate event.

event.hasConsumer

Property containing value true or false, indicating whether or not the event has a consumer.

event.consumers

Property exposing a shallow copy of all consuming functions.

event.consumerAdded(consumer)

Unmonitored eventuate representing additions of consumers. Any consumers of consumerAdded will be invoked with the consumer added to the eventuate.

Example:

var event = eventuate()
event.consumerAdded(function (eventConsumer) {
    // eventConsumer will be the consumer function
    console.log('a consumer was added to event')
})

event.consumerRemoved(consumer)

Unmonitored eventuate representing removal of consumers. Any consumers of consumerRemoved will be invoked with the consumer removed from the eventuate.

Example:

var event = eventuate()
event.consumerRemoved(function (eventConsumer) {
    // eventConsumer will be the consumer function
    console.log('a consumer was removed from event')
})

event.factory

Exposes the factory function used to create the eventuate. Example:

var eventuate = require('eventuate'),
    assert    = require('assert')

var event = eventuate()
assert(event.factory === eventuate)

newEventuate = event.filter(filterFunc)

Return a new eventuate which is a filtered subset of event. See eventuate-filter.

newEventuate = event.map(mapFunc)

Return a new eventuate which produces transformed data of event. See eventuate-map.

newEventuate = event.reduce(reduceFunc)

Return a new eventuate which produces on-goin reduced data of event. See eventuate-reduce.

var UnconsumedEventError = require('eventuate/errors').UnconsumedEventError

Constructor of error potentially thrown on eventuates with requireConsumption set.

unmonitored eventuate

If the eventuate is created with the option monitorConsumers set to false, the eventuate will not have the following properties: consumers, hasConsumer, consumerRemoved, consumerAdded. No events will be triggered when consumers are manipulated. This is used internally within eventuate for sub-events such as consumerRemoved and consumerAdded.

supporting modules

The following modules support and extend the functionality of eventuate:

• eventuate-once - act once (via callback or promise) upon the next occurrence of an eventuate
• eventuate-filter - create filtered eventuate, acting as subset of broader eventuate

install

npm install eventuate

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 test

npm run browser-test

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.