How to raise a custom event from within a JavaScript object

I am trying to get a better understanding of object orientated techniques in JavaScript.

I have the following (trivial) object:

function CustomObject () {
    this.size = 1;
};

CustomObject.prototype.addSize = function () {
    this.size += 1;
    if(this.size > 5) {
        //Raise custom Event
    }
};

And I am instating it like this.

   var myObject = new CustomObject();
    myObject.addSize();

    // Add listener for custom event from with in my Custom Object.
    // Something like this....
    myObject.addEventListener("CustomEvent", handelCustomEvent, false);
    
    function handelCustomEvent() {}

How do I raise a custom event in my custom object and then listen to that event in the parent? Is this kind of thing even possible in JavaScript?