![]() This EventEmitter object can be used to subscribe for the events. In this pattern, a constructor function returns an EventEmitter object, which was used to emit events inside a function. On the backend side, Node.js offers us the option to build a similar system using the events module. There are two common patterns that can be used to raise and bind an event using EventEmitter class in Node.js. The Node.js Event emitter If you worked with JavaScript in the browser, you know how much of the interaction of the user is handled through events: mouse clicks, keyboard button presses, reacting to mouse movements, and so on. Returns the number of listeners listening to the type of event. Raise the specified events with the supplied arguments. Event module includes EventEmitter class which can be used to raise and. Returns a copy of the array of listeners for the specified event.Įmitter.emit(event) Node.js allows us to create and handle custom events easily by using events module. Returns the current maximum listener value for the emitter which is either set by tMaxListeners(n) or defaults to faultMaxListeners. ![]() In short, the events provide easy to use customization points for the clients. ![]() By sending the events at the key points in our program execution, we let the clients add their custom logic externally at those points. Removes all listeners, or those of the specified event.īy default EventEmitters will print a warning if more than 10 listeners are added for a particular event. The Event Emitters allows us to build highly customizable components. Caution: changes array indices in the listener array behind the listener. Removes a listener from the listener array for the specified event. This listener is invoked only the next time the event is fired, after which it is removed. It can also be called as an alias of emitter.addListener()Īdds a one time listener for the event. The EventEmitter object also exposes several other methods to interact with events, like. No checks are made to see if the listener has already been added. No checks are made to see if the listener has already been added.Īdds a listener to the end of the listeners array for the specified event. Adds a listener to the end of the listeners array for the specified event.
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