addEventListener as |this|

[paulushub]

This sample is found on the Mozilla site: addEventListener

const Something = function(element) {
  // |this| is a newly created object
  this.name = 'Something Good';
  this.handleEvent = function(event) {
    console.log(this.name); // 'Something Good', as this is bound to newly created object
    switch(event.type) {
      case 'click':
        // some code here...
        break;
      case 'dblclick':
        // some code here...
        break;
    }
  };

  // Note that the listeners in this case are |this|, not this.handleEvent
  element.addEventListener('click', this, false);
  element.addEventListener('dblclick', this, false);

  // You can properly remove the listeners
  element.removeEventListener('click', this, false);
  element.removeEventListener('dblclick', this, false);
}
const s = new Something(window); // changed document.body to window for the demo

Defining a window object in C# as follows, I received the call to the addEventListener method.

public class JsSvgWindowNiL {
    public void addEventListener(string type, object listener, bool useCapture) {
        Trace.WriteLine("addEventListener(string type, object listener, bool useCapture)");

        Function listenerFunc = null;
        var listenerValue = listener as JSValue;
        if (listenerValue != null) {
            listenerFunc = listenerValue.Value as Function;
        }
    }
}

However, for the above script, the listenerValue.Value is JSObject (not Function as in all other cases). How do I invoke/call the JS handler in this case?

[nilproject]

I did not immediately understand the details of the question. As I can see, you want to invoke method handleEvent for Something. For this you should to get value of property handleEvent from object via GetProperty("handleEvent"), then cast this value to a Function and call it via Function.Call(...) with passing listener as this

[paulushub]

@nilproject Thanks for the reply. This is about integrating a scripting into an SVG rendering library. So that will be a user written script and the handleEvent method is not known to the rendering library.
When you run this script in ClearScript.V8 engine, the listener is a ScriptObject as with other listeners and calling the invoke method defined on this object instance will automatically invoke the handleEvent method, since in this case as stated in the comment,

// Note that the listeners in this case are |this|, not this.handleEvent