gistfile1.txt

function Test(cfg) {
    Test.superclass.constructor.apply(this, arguments);
    this.initializer(cfg);
};

Y.extend(Test, Y.Base, {
    initializer: function(config) {
        this.addAttrs({
            items: {
                value: []
            },
        }, config);

        Y.on("itemsChange", this.doSomething);
        items.push("item1");
    },
    doSomething: function(e) {
        Y.log("items have been changed!");
    }
}