How do you share an EventEmitter in node.js?

Question

I want to emit events from one file/module/script and listen to them in another file/module/script. How can I share the emitter variable between them without polluting the global namespace?

Thanks!

Answer 1

@srquinn is correct, you should use a shared single instance:

eventBus.js:

const EventEmitter = require('events'); const emitter = new EventEmitter();  emitter.on('uncaughtException', function (err) {     console.error(err); });  module.exports = emitter; 

Usage:

var bus = require('../path/to/eventBus');  // Register event listener bus.on('eventName', function () {     console.log('triggered!'); });  // Trigger the event somewhere else bus.emit('eventName'); 

Answer 2

You can pass arguments to require calls thusly:

var myModule = require('myModule')(Events) 

And then in "myModule"

module.exports = function(Events) {     // Set up Event listeners here } 

With that said, if you want to share an event emitter, create an emitter object and then pass to your "file/module/script" in a require call.

Update:

Though correct, this is a code smell as you are now tightly coupling the modules together. Instead, consider using a centralized event bus that can be required into each module.