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Tutte le applicazioni Node.js sono basate su un meccanismo di eventi, che determina quale funzione sarà successivamente chiamata. For more details, take a look at the implementation of the EventEmitter.įor example: var emitter = new MyEmitter() Įmitter.on('foo', () => console.log('foo event triggered')) Įmitter.on('*', () => console.log('star event triggered')) Įmitter.on('', () => console.log('catch all event triggered')) įinally, if an EventEmitter instance already exists but you want to adjust that specific instance to the new behavior, it can be easily done by patching the method at runtime like this: emitter.emit = MyEmitter.prototype. Conclusioni: ascoltare eventi con Node.js e come emetterli.
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Each event is different and tailored to the local community, varying in length and in some cases in partnership with local Node.js groups and users. We make sure to call the star ( *) event first, because in case of error events without any handlers, the result is actually an exception being thrown. Node.js Live The Node.js Foundation is kicking off a series of global events bringing together local Node.js developers around the world.
![nodejs events nodejs events](https://jelvix.com/wp-content/uploads/2018/06/node.jpg)
Here the idea is to use the star event ( *) to create handlers that gets executed on every single event (say, for logging purposes) and the empty event ( '') for a default or catch all handler, that gets executed if nothing else catches that event. Notice that the override includes a return statement, so we keep this behavior for other consumers.
Nodejs events how to#
This article will introduce the Node JS event loop mechanism and tell you how to create custom events in Node JS by example. This implementation relies on the fact that the original emit method of the EventEmitter returns true/ false depending if the event was handled by some listener or not. Node JS executes in a single process and single thread only, but the execution performance is very high because of event-driven design and callback function usage. Since Node.js v6.0.0, the new class syntax and argument spread operator is fully supported, so it's pretty safe and fairly easy to implement the desired functionality with simple inheritance and an method override: 'use strict'