gistfile1.txt

class Message{
  constructor(name) {
    this.name = name
  }
  say(serif) {
  	if(!serif) serif = "";
    console.log( this.name + ': World!' + serif);
  }
}

class Loud extends Message{
  constructor(name) {
    super( name )
  }
  loud() {
    this.say("!!!!!!!!!!!!!!!!!")
  }
}
var l = new Loud("Hello!");
l.loud(); // Hello!: World!!!!!!!!!!!!!!!!!!