Craig Condon
218 lines
9.9 KiB
HTML
218 lines
9.9 KiB
HTML
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<title>Events Node.js v0.8.14 Manual & Documentation</title>
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<h1>Node.js v0.8.14 Manual & Documentation</h1>
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<a href="index.html" name="toc">Index</a> |
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<a href="all.html">View on single page</a> |
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<a href="events.json">View as JSON</a>
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</header>
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<div id="toc">
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<h2>Table of Contents</h2>
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<ul>
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<li><a href="#events_events">Events</a><ul>
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<li><a href="#events_class_events_eventemitter">Class: events.EventEmitter</a><ul>
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<li><a href="#events_emitter_addlistener_event_listener">emitter.addListener(event, listener)</a></li>
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<li><a href="#events_emitter_on_event_listener">emitter.on(event, listener)</a></li>
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<li><a href="#events_emitter_once_event_listener">emitter.once(event, listener)</a></li>
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<li><a href="#events_emitter_removelistener_event_listener">emitter.removeListener(event, listener)</a></li>
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<li><a href="#events_emitter_removealllisteners_event">emitter.removeAllListeners([event])</a></li>
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<li><a href="#events_emitter_setmaxlisteners_n">emitter.setMaxListeners(n)</a></li>
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<li><a href="#events_emitter_listeners_event">emitter.listeners(event)</a></li>
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<li><a href="#events_emitter_emit_event_arg1_arg2">emitter.emit(event, [arg1], [arg2], [...])</a></li>
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<li><a href="#events_event_newlistener">Event: 'newListener'</a></li>
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</ul>
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</li>
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</ul>
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</li>
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</ul>
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</div>
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<div id="apicontent">
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<h1>Events<span><a class="mark" href="#events_events" id="events_events">#</a></span></h1>
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<pre><code>Stability: 4 - API Frozen</code></pre>
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<!--type=module-->
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<p>Many objects in Node emit events: a <code>net.Server</code> emits an event each time
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a peer connects to it, a <code>fs.readStream</code> emits an event when the file is
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opened. All objects which emit events are instances of <code>events.EventEmitter</code>.
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You can access this module by doing: <code>require("events");</code>
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</p>
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<p>Typically, event names are represented by a camel-cased string, however,
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there aren't any strict restrictions on that, as any string will be accepted.
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</p>
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<p>Functions can then be attached to objects, to be executed when an event
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is emitted. These functions are called <em>listeners</em>.
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</p>
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<h2>Class: events.EventEmitter<span><a class="mark" href="#events_class_events_eventemitter" id="events_class_events_eventemitter">#</a></span></h2>
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<p>To access the EventEmitter class, <code>require('events').EventEmitter</code>.
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</p>
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<p>When an <code>EventEmitter</code> instance experiences an error, the typical action is
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to emit an <code>'error'</code> event. Error events are treated as a special case in node.
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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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</p>
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<p>All EventEmitters emit the event <code>'newListener'</code> when new listeners are
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added.
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</p>
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<h3>emitter.addListener(event, listener)<span><a class="mark" href="#events_emitter_addlistener_event_listener" id="events_emitter_addlistener_event_listener">#</a></span></h3>
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<h3>emitter.on(event, listener)<span><a class="mark" href="#events_emitter_on_event_listener" id="events_emitter_on_event_listener">#</a></span></h3>
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<p>Adds a listener to the end of the listeners array for the specified event.
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</p>
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<pre><code>server.on('connection', function (stream) {
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console.log('someone connected!');
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});</code></pre>
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<h3>emitter.once(event, listener)<span><a class="mark" href="#events_emitter_once_event_listener" id="events_emitter_once_event_listener">#</a></span></h3>
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<p>Adds a <strong>one time</strong> listener for the event. This listener is
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invoked only the next time the event is fired, after which
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it is removed.
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</p>
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<pre><code>server.once('connection', function (stream) {
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console.log('Ah, we have our first user!');
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});</code></pre>
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<h3>emitter.removeListener(event, listener)<span><a class="mark" href="#events_emitter_removelistener_event_listener" id="events_emitter_removelistener_event_listener">#</a></span></h3>
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<p>Remove a listener from the listener array for the specified event.
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<strong>Caution</strong>: changes array indices in the listener array behind the listener.
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</p>
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<pre><code>var callback = function(stream) {
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console.log('someone connected!');
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};
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server.on('connection', callback);
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// ...
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server.removeListener('connection', callback);</code></pre>
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<h3>emitter.removeAllListeners([event])<span><a class="mark" href="#events_emitter_removealllisteners_event" id="events_emitter_removealllisteners_event">#</a></span></h3>
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<p>Removes all listeners, or those of the specified event.
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</p>
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<p>Note that this will <strong>invalidate</strong> any arrays that have previously been
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returned by <code>emitter.listeners(event)</code>.
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</p>
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<h3>emitter.setMaxListeners(n)<span><a class="mark" href="#events_emitter_setmaxlisteners_n" id="events_emitter_setmaxlisteners_n">#</a></span></h3>
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<p>By default EventEmitters will print a warning if more than 10 listeners are
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added for a particular event. 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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</p>
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<h3>emitter.listeners(event)<span><a class="mark" href="#events_emitter_listeners_event" id="events_emitter_listeners_event">#</a></span></h3>
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<p>Returns an array of listeners for the specified event.
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</p>
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<pre><code>server.on('connection', function (stream) {
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console.log('someone connected!');
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});
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console.log(util.inspect(server.listeners('connection'))); // [ [Function] ]</code></pre>
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<p>This array <strong>may</strong> be a mutable reference to the same underlying list of
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listeners that is used by the event subsystem. However, certain
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actions (specifically, removeAllListeners) will invalidate this
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reference.
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</p>
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<p>If you would like to get a copy of the listeners at a specific point in
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time that is guaranteed not to change, make a copy, for example by doing
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<code>emitter.listeners(event).slice(0)</code>.
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</p>
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<p>In a future release of node, this behavior <strong>may</strong> change to always
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return a copy, for consistency. In your programs, please do not rely on
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being able to modify the EventEmitter listeners using array methods.
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Always use the 'on' method to add new listeners.
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</p>
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<h3>emitter.emit(event, [arg1], [arg2], [...])<span><a class="mark" href="#events_emitter_emit_event_arg1_arg2" id="events_emitter_emit_event_arg1_arg2">#</a></span></h3>
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<p>Execute each of the listeners in order with the supplied arguments.
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</p>
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<h3>Event: 'newListener'<span><a class="mark" href="#events_event_newlistener" id="events_event_newlistener">#</a></span></h3>
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<div class="signature"><ul>
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<li><code>event</code> <span class="type">String</span> The event name</li>
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<li><code>listener</code> <span class="type">Function</span> The event handler function</li>
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</div></ul>
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<p>This event is emitted any time someone adds a new listener.
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</p>
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<p>Copyright <a href="http://joyent.com/">Joyent, Inc</a>, Node.js is a <a href="/trademark-policy.pdf">trademark</a> of Joyent, Inc. View <a href="https://raw.github.com/joyent/node/v0.8.14/LICENSE">license</a>.</p>
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