将侦听器添加到MVCObject JavaScript

Question

我已经实现了此MVCObject Library，但是有一个问题，单击按钮后事件不会触发更改，您能突出显示问题吗？

ObjectA.prototype = new MVCObject();
var object_a = new ObjectA();

ObjectA.prototype.foo_changed = function()
{
console.log('ObjectA foo changed, it is now: ' + this.get('foo'));
};

//  Not working Hook
object_a.changed('foo', () => {
console.log('===> index.js ===> Need to be Fired');
})

$(function(){

$('#btn-panel').click(function(){

    object_a.set('foo', 'I am cool');
});
});

附加的侦听器挂钩不起作用，因此正在寻找类似的内容。

object_a.on('foo_changed', function() {
      console.log('===> index.js ===> First Listener');
})

object_a.on('foo_changed', function() {
      console.log('===> index.js ===> Second Listener');
})

谢谢