Why use `eventEmitter` instead of promise

Question

I've found the following example in a book I'm reading:

function User() {
    EventEmitter.call(this);
    this.addUser = function (username, password) {
        // add the user
        // then emit an event
        this.emit("userAdded", username, password);
    };
}

var user = new User();
var username = "colin";
var password = "password";

user.on("userAdded", function(username, password) {
    console.log("Added user " + username);
});

user.addUser(username, password);

It seems to me that using EventEmitter is completely redundant here. Promises would do a much better job:

function User() {
    this.addUser = function (username, password) {
        return new Promise(function (resolve) {
            // add the user
            // and resolve
            resolve();
        });
    };
}

and the usage:

user.addUser(username, password).then(function(username, password) {
    console.log("Added user " + username);
});

Does using EventEmitter have any advantages over using Promises or it's simply the code from the time when Promises where not available? Or is this style is not welcomed in node.js?

Answer 1

Main differences between EventEmitter and Promise in point, that Promise can be fulfilled only once whereas events can be triggered any number of times