EventEmitter

The last EventEmitter you'll ever need. Small, fast, full-featured, for node.js and the browser.
Apart from the usual stuff, EventEmitter features:

handleEvent() objects
wildcards
namespaces
an API you already know
excellent documentation
extensive tests, powered by Jasmine (v2.1)
support for your package manager

And all this in 3.2kB (minified) or 1050 bytes (gzipped)!

Getting a copy
- Source
- NPM
- Bower
- Component
Using it in your page
Contributing
Notes
- Wildcards
- Listeners
API
License

Getting a copy

There are several ways of obtaining a copy of EventEmitter. You can download the source code from GitHub, or use your preferred package manager.

Source

Go to the GitHub repo, download the EventEmitter.js or EventEmitter.min.js (minified) scripts and put them somewhere in your project folder.

NPM

Make sure you have node.js and npm (which comes with node.js) installed. Then, you can just:

$ npm install --save last-eventemitter

Bower

Make sure you have Bower installed. Then, you can just:

$ bower install TuurDutoit/EventEmitter

Component

Make sure you have Component installed. Then, you can just:

$ component install TuurDutoit/EventEmitter

Using it in your page

Again, there are several ways to do this. EventEmitter works with AMD loaders (like requirejs), commonJS (used by node.js) and in the browser, as the global EventEmitter symbol.

Browser

Just include the EventEmitter.js (developement) or EventEmitter.min.js (production) scripts in your page, by appending a <script> tag in the <head>:

<script type="text/javascript" src="path/to/EventEmitter.js"></script>

AMD

Just require it in your code, like so:

//myModule.js
define("path/to/EventEmitter", function(EventEmitter) {...});

Note the absence of the .js extension on path/to/EventEmitter!

node.js / commonJS

Just require it in your code, like so:

var EventEmitter = require("last-eventemitter");

Note the absence of the .js extension on path/to/EventEmitter!

Contributing

EventEmitter is fully open-source and free as in speech. Please feel free to open issues (in the issue tracker please) and don't be shy to open a Pull Request! Happy coding!

Notes

Wildcards

At the moment the wildcards implementation works with RegExps, which have one major downside: comparing two RegExps (and thus wildcard events) is very difficult. That is why I advise you to use wildcards only with namespaces: use them to wildcard scopes, but not parts of scopes/events. That leads to problems when matching event strings.

Also, wildcards work differently with #off() and #offAll() than with all the other methods. With #off() and #offAll(), the events passed to those methods are converted to RegExps, and then all the listeners' event strings are matched against these RegExps to determine which should be removed. This prevents the removal of a listener listening to scope:* by calling #offAll("scope:event"), but allows removing a listener listening for scope:event byt calling #offAll("scope:*").
With all the other methods, it works a little differently. Here, matches are tested in both ways: the listeners' event strings are matched against the events RegExp, and the event is tested against the listeners' RegExps. This allows executing a listener listening to scope:* with a call to emit("scope:event"), but it also allows executing one listening to scope:event by calling emit("scope:*").

I'm working on a way to allow for more complex wildcards, maybe even using RegExps yourself in all the methods, but that is complex, and more importantly, computationally intensive, and thus slow. I hope I can solve the problem, but don't expect that to happen soon.

Listeners

Listeners can be either a normal function or an object with a handleEvent() method (as in the DOM Events API). For more info about handleEvent(), check this page (check the 'listener' section).

API

Note: A . means a property/method is only available on the EventEmitter object, not on its instances. A # means that a property/method is only available on EventEmitter instances.

Note: A Listener type means either a normal function or an Object with a handleEvent() method. For more info, check the Listeners section above.

new EventEmitter()

return: EventEmitter. Of course.

To begin, create a new instance of EventEmitter. The contructor doesn't expect any arguments.

var ee = new EventEmitter();

#_events | Object

The #_eventsobject maps event strings to arrays of listeners. It is intended to be used internally, but you can, very cautiously, use it yourself.

An _events object looks like this:

ee._events = {
    "event": [function(){...}, function(){...}, function(){...}],
    "scope:event": [function(){...}],
    "scope:*": [function(){...}, function(){...}]
}

#on/addListener/addEventListener (string: event, Listener: listener)

event: string. The event to add the listener to. May contain wildcards.
listener: Listener. The listener to add.
return: EventEmitter. For chaining.

Use this method to attach an event listener. When the event is fired, the listener will be executed (i.e. passed to EventEmitter.execListener) and the arguments passed to emit() will be passed on to the listener. The last argument will be the event string passed to emit(). If a listener is added multiple times, it will be executed the same amount of times it was added and in the same order as it was added. Also, event may contain wildcards (please read the Wildcards section).

// Received event: scope:event
// Hello, Tuur Dutoit
ee.on("event", function(name, event) {
    console.log("Hello, " + name);
});
ee.on("scope:*", function(event) {
    console.log("Received event: " + event);
});
 
ee.emit("scope:event");
ee.emit("event", "Tuur Dutoit");

#once/addOnceListener (string: event, Listener: listener)

event: string. The event to add the listener to. May contain wildcards.
listener: Listener. The listener to add.
return: EventEmitter. For chaining.

This method does the same as #on(), but it makes sure the listener is only called once: it will remove it after the first call.

// Listener called 1 time.
// Done.
var count = 0;
ee.once("event", function() {
    count++;
    console.log("Listener called " + count + " time.");
});
 
ee.emit("event");
ee.emit("event");
console.log("Done.");

#many/addManyListener (string: event, Listener: listener, int: times)

event: string. The event to add the listener to. May contain wildcards.
listener: Listener. The listener to add.
times: int. The maximum amount of times to call the listener.
return: EventEmitter. For chaining.

This method does the same as #on(), but makes sure the listener is called a maximum of times times, by removing the listener after the timesth call.

Note: addManyListener is singular!

// Listener called 1 times.
// Listener called 2 times.
// Done.
var count = 0;
ee.many("event", function() {
    count++;
    console.log("Listener called " + count + " times.");
}, 2);
 
ee.emit("event");
ee.emit("event");
ee.emit("event");
console.log("Done.");

#emit/fire/trigger (string: event, [any: arg1, any: arg2,...])

event: string. The event that should be emitted. May contain wildcards.
argN: any. Arguments to pass to the listeners.
return: EventEmitter. For chaining.

This method emits events, i.e. it executes all the listeners that are listening for event (which may contain wildcards; read the Wildcards section), passing in all the arguments after event.
There are two things happening here:

Checking which listeners to call. This is done by checking if the event RegExp matches the listener's event string, or vice versa. Read the Wildcards section for more info.
Executing the listeners. In this stage, all the matching listeners are passed to .execListener() for execution. The args will be set to any arguments that are passed after event, and then event itself is passed as last argument.

// Received event: scope:event
// Hello, Tuur Dutoit
ee.on("event", function(name, event) {
    console.log("Hello, " + name);
});
ee.on("scope:*", function(event) {
    console.log("Received event: " + event);
});
 
ee.emit("scope:event");
ee.emit("event", "Tuur Dutoit");

#off/removeListener/removeEventListener (string:event, Listener: listener, [bool: all (false)])

event: string. The event to remove the listener from. May contain wildcards.
listener: Listener. The listener to remove.
all: bool, optional (false). Whether to remove all instances of the listener.
return: EventEmitter. For chaining.

This method removes listener from the list of listeners for event. event may contain wildcards, but these work a little different from #on() and #emit(): here, only the listeners' event strings are matched against event's RegExp, and not the other way around. For more info, read the Wildcards section.
The all argument allows to control the behaviour when a listener has been added multiple times. When all is false (the default), only one instance of the listener is removed. When all is true, all the instances (that match event) will be removed.

With all = false:

var listener = function(){...};
// Add the listener twice
ee.on("event", listener);
ee.on("event", listener);
// Remove one instance
ee.off("event", listener);
// 1
ee.count("event");

With all = true:

ee.on("event", listener);
ee.on("event", listener);
// Remove all instances
ee.off("event", listener, true);
// 0
ee.count("event");

#offAll/removeAllListeners ([string: event ("*")])

event: string, optional ("*"). The event to remove all listeners from. May contain wildcards.
return: EventEmitter. For chaining.

This method removes all listeners for a specific event (which may contain wildcards; read the Wildcards section), or for the whole EventEmitter (if no event is specified).

For a specific event:

ee.on("event", function(){...});
ee.on("other-event", function(){...});
ee.removeAllListeners("event");
 
// 1
ee.count("event");

For the whole EventEmitter:

ee.on("event", function(){...});
ee.on("other-event", function(){...});
ee.offAll();
 
// 0
ee.count();

#count/countListeners ([string: event ("*")])

event: string, optional ("*") The event for which to count the listeners. May contain wildcards.
return: int The amount of listener listening for event.

This method counts the listeners that are listening to event (which may contain wildcards; read the Wildcards section). If no event is specified, it counts all the listeners for the EventEmitter.

For a specific event:

ee.on("event", function(){...});
ee.on("other-event", function(){...});
 
// 1
ee.count("event");

For the whole EventEmitter:

ee.on("event", function(){...});
ee.on("other-event", function(){...});
 
// 2
ee.count();

#listeners/getListeners ([string: event ("*")])

event: string, optional ("*"). The event to get the listeners for. May contain wildcards.
return: Array<Listener>. An array containing all the listeners listening for event.

This method retrieves all the listeners that listen for event (which may contain wildcards; read the Wildcards section). If no event is specified, it returns all the listeners bound to the EventEmitter. The returned array may contain duplicates (if you added a listener more than once).

For a specific event:

ee.on("event", function listener1(){...});
ee.on("other-event", function listener2(){...});
 
// [ function listener1(){...} ]
ee.listener("event");

For the whole EventEmitter:

ee.on("event", function listener1(){...});
ee.on("other-event", function listener2(){...});
 
// [ function listener1(){...}, function listener2(){...} ]
ee.listeners();

.execListener (Listener: listener, Array<any>: args)

listener: Listener The listener to execute.
args: Array<any> The arguments to pass to the listener
return: any. Anything the listener returns.

Note: This method is only available on the EventEmitter object, not on its instances!

EventEmitter.execListener() executes a listener, apply()ing args to it.
listener can be a function, or an object with a handleEvent() method. For more info about listeners, check the Listeners section. The this in the listener will be set to listener (be it a function or an object; this is default javascript behaviour). This method is intended for internal use, but may be used publicly.

var listener = function(arg1, arg2){
    console.log(arg1 + ", " + arg2);
    console.log(this);
}
var objectListener = {
    handleEvent: listener
}
var args = ["hello", "world"];
 
//hello, world
//function
EventEmitter.execListener(listener, ["hello", "world"]);
 
//hello, world
//object
EventEmitter.execListener(objectListener, ["hello", "world"]);

.eventRegexp (string: event)

event: string. The event name to convert to a RegExp.
return: RegExp. The RegExp that matches the event name.

Note: This method is only available on the EventEmitter object, not on its instances!

With EventEmitter.eventRegexp(), you can get the RegExp representation of a wildcard event. This method just passes the event name you give it to new RegExp(event), after replacing * by .*. This method is intended for internal use, but may be used publicly.
This method uses the EventEmitter.regexps object as a sort of cache: any event strings that have not yet passed eventRegexp() will be added to it (with their RegExp representation), and EventRegexp() will return the RegExp that has been stored in regexps if the event string can be found there.

Note: When matching wildcard events with other wildcard events, weird things can happen. I'm working on a way to solve this. In the meantime, take a look at the Wildcards section.

// /scope:.*/
EventEmitter.eventRegexp("scope:*");
// Matches: "scope:event", "scope:other-event"
// but not: "event", "world:event"

.regexps | Object

Note: This property is only available on the EventEmitter object, not on its instances!

EventEmitter.regexps is an object matching event strings and their RegExp representations. This is only used by EventEmitter.eventRegexp() as a sort of cache, to prevent memoty leaks.

It looks like this:

EventEmitter.regexps = {
    "event": /^event$/,
    "scope:*": /^scope:.*$
}

License

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

last-eventemitter

EventEmitter

Table of Contents

Getting a copy

Source

NPM

Bower

Component

Using it in your page

Browser

AMD

node.js / commonJS

Contributing

Notes

Wildcards

Listeners

API

new EventEmitter()

#_events | Object

#on/addListener/addEventListener (string: event, Listener: listener)

#once/addOnceListener (string: event, Listener: listener)

#many/addManyListener (string: event, Listener: listener, int: times)

#emit/fire/trigger (string: event, [any: arg1, any: arg2,...])

#off/removeListener/removeEventListener (string:event, Listener: listener, [bool: all (false)])

#offAll/removeAllListeners ([string: event ("*")])

#count/countListeners ([string: event ("*")])

#listeners/getListeners ([string: event ("*")])

.execListener (Listener: listener, Array<any>: args)

.eventRegexp (string: event)

.regexps | Object

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