NodeJS EventEmitter Tutorial
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var fs = require('fs'); // Create a stream to read file var rs = fs.createReadStream('C:/test/demo.txt'); // The event 'open': rs.on('open', function() { console.log('File opened!'); });
Listener

// Import events module var events = require('events'); // Create an EventEmitter object var eventEmitter = new events.EventEmitter();
// Add Event Listener eventEmitter.addListener('bellRing', bellRingHandler1); // Add Event Listener eventEmitter.addListener('bellRing', bellRingHandler2);
// Fire bellRing event!! eventEmitter.emit('bellRing', 'Jerry');

// Import events module var events = require('events'); // Create an eventEmitter object var eventEmitter = new events.EventEmitter(); // A Listener var bellRingHandler1 = function bellRingHandler1(who) { console.log("\n"); console.log('The Bell Ringing..... (Handler 1)'); console.log(" " + who + " was standing behind the door!"); if(who == 'Jerry') { console.log(' Tom, help me!!'); return; } console.log(" Welcome " + who); } // A Listener var bellRingHandler2 = function bellRingHandler2(who) { console.log("\n"); console.log('The Bell Ringing..... (Handler 2)'); eventEmitter.emit("nobodyIsAtHome"); } // A Listener var nobodyIsAtHomeHandler = function nobodyIsAtHomeHandler() { console.log("\n"); console.log(" Sorry, Nobody is at home now, Please leave your message!") } // Add Event Listeners eventEmitter.addListener('bellRing', bellRingHandler1); eventEmitter.addListener('bellRing', bellRingHandler2); eventEmitter.addListener('nobodyIsAtHome', nobodyIsAtHomeHandler); // ----- Testing ------ // Fire bellRing event!! eventEmitter.emit('bellRing', 'Jerry');
node eventemitter-examples/first-example.js

No | Method | Description |
---|---|---|
1 | addListener(event, listener) | Add a listener the end of the listeners array for the specified event. This method doesn't check whether this listener has ever been added or not. |
2 | on(event, listener) | Exactly, this method is 100% identical to the addListener method. |
3 | once(event, listener) | Add a listener to the listeners array of the specified event. But this listener is only called one time when an event happens. After that it is removed from the array. |
4 | removeListener(event, listener) | Remove a listener from the listeners array of the specified event. If a listener has been added to this array many times. To remove this listener fully, you need to call this method many times. |
5 | removeAllListeners([event]) | Remove all listeners, or remove all listeners of an event designated. |
6 | setMaxListeners(n) | By default, EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default which helps finding memory leaks. Obviously not all Emitters should be limited to 10. You can set a different number, or set to zero for unlimited. |
7 | listeners(event) | Return a listeners array to the specified event. |
8 | emit(event, [arg1], [arg2], [...]) | Executes each listener in the array in turn, with parameters. Return true if the array has at least one listener. On the contrary, return false. |