Create custom (this.on) events from event window.addEventListener

Question

I'm trying to intercept some window.addEventListener inside custom "this.on events".

I am trying with this code, I have no idea how to get my result :(

(i receive correctly the window.addEventListener)

Anyone have any ideas?

Function

function playersdk(...){


  window.addEventListener('message', ({ data }) => {
    let eventData = JSON.parse(data);
    this.on = function (event, obj) {

        console.log(eventData);
        if (event == eventData.type) {
            return eventData;
        }
    }
    
  });

}

main page

let player=new playersdk();
player.on('play', e => console.log('play'));