Dfyjkt

Here is an event listener added, if I want to test if this event listener is working or not, how do I test? window.postMessage doesn't seem to be triggering this event. Basically, how do I trigger "some_event" so that my EventListener runs.

window.addEventListener('some_event', function() 
console.log("some_event triggered");
 );

Please note, I was able to reproduce with "click" event, but what I want to know is, how do I know if any string is passed as an event. Example:

window.addEventListener('add_to_cart', function() 
console.log("some_event triggered");
 );

So I would like to simulate this event listener to check if it's working or not. How do I test this.

You need to use some concrete event name like for example click - and click on browser page window - eg:

window.addEventListener('click', function() 
 console.log("some_event triggered");
);

Here is some info about events and situations when they are trigger.

After question update

Yes you can define and fire arbitrary events - read here. And here is some example code:

var event = new Event('some_event');

// Listen for the event.
window.addEventListener('some_event', function (e) 
 console.log('some_event triggered') 
, false);

// Dispatch the event.
window.dispatchEvent(event);

So you fire event using window.dispatchEvent(event) and this is the way you can test it.

You can trigger an event using dispatchEvent and fireEvent in IE.

 var ev, element = window;
 if (document.createEvent) 
 ev = document.createEvent("HTMLEvents");
 ev.initEvent("eventname", true, true);
 ev.eventName = "eventname";
 element.dispatchEvent(ev);
 else 
 ev = document.createEventObject();
 ev.eventType = "eventname";
 ev.eventName = "eventname";
 element.fireEvent("on" + ev.eventType, event);
 

function triggerEvent(elem, name)
 var ev;
 if (document.createEvent) 
 ev = document.createEvent("HTMLEvents");
 ev.initEvent(name, true, true);
 ev.eventName = name;
 elem.dispatchEvent(ev);
 else 
 ev = document.createEventObject();
 ev.eventType = name;
 ev.eventName = name;
 elem.fireEvent("on" + ev.eventType, event);
 

window.addEventListener("click", function(e)
 console.log("Clicked");
);
window.addEventListener("custom_event", function(e)
 console.log("custom_event triggered");
);
triggerEvent(window, "click");
triggerEvent(window, "custom_event");