Example node event emitter setup from neveraw.us

app.js

var pb = new PhoneBook('asdf.txt');
pb.on('error', function(error) {
    console.log(error);
});
pb.on('data', function(data) {
    console.log(data);
});

core.js

var events = require('events'),
    sys = require('sys');
var PhoneBook = function(bookFile) {
    var fs = require('fs'),
        self = this;

    events.EventEmitter.call(this);

    fs.readFile(this.bookFile, function(err, data) {
        if(err) {
            self.emit('error', err);
        } else {
            self.emit('data', data.split('\n'));
        } 
    });
};
sys.inherits(PhoneBook, events.EventEmitter);