what are event emitters in node js code example

Example: node js event emitter

const EventEmitter = require('events');

class MyEmitter extends EventEmitter {
  foo() {
    this.emit('test');
  }
}
const myEmitter = new MyEmitter();
myEmitter.on('test', () => console.log('Yay, it works!'));

myEmitter.foo();	// Yay it works!