249 lines
7.1 KiB
Markdown
249 lines
7.1 KiB
Markdown
[](https://www.codeship.io/projects/11259)
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# SYNOPSIS
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EventEmitter2 is an implementation of the EventEmitter found in Node.js
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# DESCRIPTION
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### FEATURES
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- Namespaces/Wildcards.
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- Times To Listen (TTL), extends the `once` concept with `many`.
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- Browser environment compatibility.
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- Demonstrates good performance in benchmarks
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```
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EventEmitterHeatUp x 3,728,965 ops/sec \302\2610.68% (60 runs sampled)
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EventEmitter x 2,822,904 ops/sec \302\2610.74% (63 runs sampled)
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EventEmitter2 x 7,251,227 ops/sec \302\2610.55% (58 runs sampled)
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EventEmitter2 (wild) x 3,220,268 ops/sec \302\2610.44% (65 runs sampled)
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Fastest is EventEmitter2
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```
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### Differences (Non breaking, compatible with existing EventEmitter)
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- The constructor takes a configuration object.
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```javascript
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var EventEmitter2 = require('eventemitter2').EventEmitter2;
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var server = new EventEmitter2({
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//
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// use wildcards.
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//
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wildcard: true,
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//
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// the delimiter used to segment namespaces, defaults to `.`.
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//
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delimiter: '::',
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//
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// if you want to emit the newListener event set to true.
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//
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newListener: false,
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//
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// max listeners that can be assigned to an event, default 10.
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//
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maxListeners: 20
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});
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```
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- Getting the actual event that fired.
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```javascript
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server.on('foo.*', function(value1, value2) {
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console.log(this.event, value1, value2);
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});
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```
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- Fire an event N times and then remove it, an extension of the `once` concept.
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```javascript
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server.many('foo', 4, function() {
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console.log('hello');
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});
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```
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- Pass in a namespaced event as an array rather than a delimited string.
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```javascript
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server.many(['foo', 'bar', 'bazz'], function() {
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console.log('hello');
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});
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```
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# API
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When an `EventEmitter` instance experiences an error, the typical action is
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to emit an `error` event. Error events are treated as a special case.
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If there is no listener for it, then the default action is to print a stack
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trace and exit the program.
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All EventEmitters emit the event `newListener` when new listeners are
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added.
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**Namespaces** with **Wildcards**
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To use namespaces/wildcards, pass the `wildcard` option into the EventEmitter
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constructor. When namespaces/wildcards are enabled, events can either be
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strings (`foo.bar`) separated by a delimiter or arrays (`['foo', 'bar']`). The
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delimiter is also configurable as a constructor option.
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An event name passed to any event emitter method can contain a wild card (the
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`*` character). If the event name is a string, a wildcard may appear as `foo.*`.
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If the event name is an array, the wildcard may appear as `['foo', '*']`.
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If either of the above described events were passed to the `on` method,
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subsequent emits such as the following would be observed...
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```javascript
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emitter.emit('foo.bazz');
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emitter.emit(['foo', 'bar']);
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```
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### emitter.addListener(event, listener)
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### emitter.on(event, listener)
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Adds a listener to the end of the listeners array for the specified event.
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```javascript
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server.on('data', function(value1, value2, value3, ...) {
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console.log('The event was raised!');
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});
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```
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```javascript
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server.on('data', function(value) {
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console.log('The event was raised!');
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});
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```
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### emitter.onAny(listener)
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Adds a listener that will be fired when any event is emitted.
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```javascript
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server.onAny(function(value) {
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console.log('All events trigger this.');
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});
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```
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### emitter.offAny(listener)
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Removes the listener that will be fired when any event is emitted.
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```javascript
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server.offAny(function(value) {
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console.log('The event was raised!');
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});
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```
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#### emitter.once(event, listener)
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Adds a **one time** listener for the event. The listener is invoked
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only the first time the event is fired, after which it is removed.
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```javascript
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server.once('get', function (value) {
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console.log('Ah, we have our first value!');
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});
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```
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### emitter.many(event, timesToListen, listener)
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Adds a listener that will execute **n times** for the event before being
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removed. The listener is invoked only the first **n times** the event is
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fired, after which it is removed.
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```javascript
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server.many('get', 4, function (value) {
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console.log('This event will be listened to exactly four times.');
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});
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```
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### emitter.removeListener(event, listener)
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### emitter.off(event, listener)
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Remove a listener from the listener array for the specified event.
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**Caution**: changes array indices in the listener array behind the listener.
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```javascript
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var callback = function(value) {
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console.log('someone connected!');
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};
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server.on('get', callback);
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// ...
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server.removeListener('get', callback);
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```
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### emitter.removeAllListeners([event])
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Removes all listeners, or those of the specified event.
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### emitter.setMaxListeners(n)
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By default EventEmitters will print a warning if more than 10 listeners
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are added to it. This is a useful default which helps finding memory leaks.
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Obviously not all Emitters should be limited to 10. This function allows
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that to be increased. Set to zero for unlimited.
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### emitter.listeners(event)
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Returns an array of listeners for the specified event. This array can be
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manipulated, e.g. to remove listeners.
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```javascript
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server.on('get', function(value) {
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console.log('someone connected!');
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});
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console.log(server.listeners('get')); // [ [Function] ]
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```
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### emitter.listenersAny()
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Returns an array of listeners that are listening for any event that is
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specified. This array can be manipulated, e.g. to remove listeners.
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```javascript
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server.onAny(function(value) {
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console.log('someone connected!');
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});
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console.log(server.listenersAny()[0]); // [ [Function] ]
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```
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### emitter.emit(event, [arg1], [arg2], [...])
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Execute each of the listeners that may be listening for the specified event
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name in order with the list of arguments.
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# LICENSE
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(The MIT License)
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Copyright (c) 2011 hij1nx <http://www.twitter.com/hij1nx>
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the 'Software'), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is furnished
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to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
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AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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