Adds a one-time listener function for the event named eventName. The
next time eventName is triggered, this listener is removed and then invoked.
server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});
Returns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. The
emitter.prependOnceListener() method can be used as an alternative to add the
event listener to the beginning of the listeners array.
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
The callback function
Adds the
listenerfunction to the end of the listeners array for the event namedeventName. No checks are made to see if thelistenerhas already been added. Multiple calls passing the same combination ofeventNameandlistenerwill result in thelistenerbeing added, and called, multiple times.Returns a reference to the
EventEmitter, so that calls can be chained.By default, event listeners are invoked in the order they are added. The
emitter.prependListener()method can be used as an alternative to add the event listener to the beginning of the listeners array.