CODEWITHSUNDEEP
javascriptnode.jseventsevent-handlingeventemitter
YulePale
YulePale

Reputation: 7686

Calling the event emitter before the event handler in nodejs

I am going through this code and I have seen the nodejs event emitter being called before the event handler was defined(this line and this line).

When I try to replicate the same, no event gets handled.

    eventEmitter.emit('event');

    eventEmitter.on('event', () => {
        console.log('event handled');
    });

When you put the event emitter after the event handler 'event handled ' gets logged.

Is the code on GitHub wrong? Or does it still work because it is in a module and there is a way the module is imported that allows it to work? Kindly explain. Thank you.

Upvotes: 0

Views: 928

Answers (1)

mb_s88
mb_s88

Reputation: 392

The event emission on line 44 is inside of the handler being bound to the ioChat's "connection" event which is not invoked before the binding of eventEmitter's "get-all-users" event on line 181. So even though the line where the event is invoked comes first, it will not be invoked first.

Example:

eventEmitter.on('connection', () => {
  console.log('this should log second');
  eventEmitter.emit('someEvent');
});

eventEmitter.on('someEvent', () => {
  console.log('this should log third');
});

console.log('this should log first');
eventEmitter.emit('connection');

Upvotes: 2

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