mqemitter [](https://travis-ci.org/mcollina/mqemitter)
=================================================================
An Opinionated Message Queue with an emitter-style API, but with
callbacks.
* Installation
* Basic Example
* API
* Wildcards
* Licence & copyright
If you need a multi process MQEmitter, check out the table below:
[](https://github.com/feross/standard)
## Installation
```
$ npm install mqemitter --save
```
## Basic Example
```js
var mq = require('mqemitter')
var emitter = mq({ concurrency: 5 })
var message
emitter.on('hello world', function (message, cb) {
// call callback when you are done
// do not pass any errors, the emitter cannot handle it.
cb()
})
// topic is mandatory
message = { topic: 'hello world', payload: 'or any other fields' }
emitter.emit(message, function () {
// emitter will never return an error
})
```
## API
* MQEmitter
* emitter#emit()
* emitter#on()
* emitter#removeListener()
* emitter#close()
* emitter#closed
-------------------------------------------------------
### MQEmitter(opts)
MQEmitter is the class and function exposed by this module.
It can be created by `MQEmitter()` or using `new MQEmitter()`.
An MQEmitter accepts the following options:
- `concurrency`: the maximum number of concurrent messages that can be
on concurrent delivery.
- `wildcardOne`: the char that will match one level wildcards.
- `wildcardSome`: that char that will match multiple level wildcards.
- `separator`: the separator for the different levels.
For more information on wildcards, see [this explanation](#wildcards) or
[Qlobber](https://github.com/davedoesdev/qlobber).
-------------------------------------------------------
### emitter.emit(message, callback())
Emit the given message, which must have a `topic` property, which can contain wildcards
as defined on creation.
-------------------------------------------------------
### emitter.on(topic, callback(message, done), [onDone(err)])
Add the given callback to the passed topic. Topic can contain wildcards,
as defined on creation.
The `callback`, accept two parameters, the passed message and a `done`
callback.
The callback __must never error__ and `done` must not be called with an
__`err`__ object.
`onDone` will be called when the event subscribe is done correctly.
-------------------------------------------------------
### emitter.removeListener(topic, callback(message, done), [removeDone(err)])
The inverse of `on`.
-------------------------------------------------------
### emitter.close(callback())
Close the given emitter. After, all writes will return an error.
## Wildcards
__MQEmitter__ supports the use of wildcards: every topic is splitted
according to `separator` (default `/`).
The wildcard character `+` matches exactly one word:
```javascript
var mq = require('mqemitter')
, emitter = mq()
emitter.on('hello/+/world', function(message, cb) {
// this will print { topic: 'hello/my/world', 'something': 'more' }
console.log(message)
cb()
})
emitter.on('hello/+', function(message, cb) {
// this will not be called
console.log(message)
cb()
})
emitter.emit({ topic: 'hello/my/world', something: 'more' })
```
The wildcard character `#` matches zero or more words:
```javascript
var mq = require('mqemitter')
, emitter = mq()
emitter.on('hello/#', function(message, cb) {
// this will print { topic: 'hello/my/world', 'something': 'more' }
console.log(message)
cb()
})
emitter.on('#', function(message, cb) {
// this will print { topic: 'hello/my/world', 'something': 'more' }
console.log(message)
cb()
})
emitter.on('hello/my/world/#', function(message, cb) {
// this will print { topic: 'hello/my/world', 'something': 'more' }
console.log(message)
cb()
})
emitter.emit({ topic: 'hello/my/world', something: 'more' })
```
Of course, you can mix `#` and `+` in the same subscription.
## LICENSE
MIT