title: Set event listeners in ES6 class definition that extends EventEmitter
body: <p>I want some predefined custom listeners, that are defined already with the <strong>definition</strong> of the class (like the build in <a href="https://nodejs.org/api/events.html#events_event_newlistener" rel="noreferrer"><code>'newListner'</code></a> event). So I don't want to just bind them in the constructor because it would be executed on every new instance of that class.</p>
  
  <p>How to do this? Modify the prototype? Is it possible at all?</p>
  
  <p>What I have so far:</p>
  
  <pre><code>class Cat extends EventEmitter {
    // just added for demonstration, I don't want this!
    constructor() {
      super();
      // does fire
      this.on('wave', function() { console.log('constructor wave'); });
    }
  }
  // compiles but does not fire
  Cat.prototype.on('wave', function() { console.log('prototype wave'); });
  
  var cat = new Cat();
  cat.emit('wave');
  </code></pre>