Ruby on Rails

I am reading the Active Storage documentation available here and I am trying to find out how to display a progress bar. Just to test I added the following code inside my application.js

The image gets uploaded on amazon just fine but I see nothing in browser's console

	addEventListener("direct-upload:initialize", doSomething, false);    	function doSomething(e) {  		alert("Event is called: " + e.type);  	}  

I also tried this but I do not see anything in console.

document.getElementById("image_form").addEventListener("direct-upload:initialize", function() {    console.log('direct-uploads:initialize')  });    document.getElementById("image_form").addEventListener("direct-uploads:end", function() {    console.log('direct-uploads:start')  });  

I would like to know how to make use of the events available? 

Any help will be really appreciated as I am really stuck and cant find any material on how to do this.