dart - Dynamically adding event listeners by name -

How do you translate this function from javascript to dart?

  function addEvtListener (element L, evtName, fn) {return el.addEventListener? El.addEventListener (evtName, fn, false): el.attachEvent ('+' + evtName, fn); }   
 The main issue event name is dynamic. I can clearly call:  
  el.onclick.listen ((event) => fn (event));   
 If  evtName  is a click event, but is there any way in dart?  
  l.on ("click"). Listen (event) = & gt; Fn (incident));    
 
 
 An overview of the various methods of listening for an event in the document of the events class is named :  
 You will see that you can do both:  
  New EventStream Provider (evtName) .forTaget (el) listen (F) N);   
 or  
  el.on [evtName] .listen (fn);