gistfile1.txt

function Thing(socket) {
    this.socket = socket;
    this.socket.once('end', this.cleanup.bind(this));
    
    this.handlers = [ ];
}
Thing.prototype.onDisconnect = function (cb) {
    this.handlers.push(cb);
}
Thing.prototype.cleanup = function () {
    return Promise.reduce(this.handlers, function (retVal, handler) {
        return handler(retVal);
    }, 'initialValue')
    .then(function (finalValue) {
        // do whatever you want
    });
}