My ES6 class definition proposal

class_example.js

// How about another ES6 class definition proposal? :-)

// What if the the `class` block is a closure?
class Monster extends Sprite {
  
  // This is a block/closure so this creates a local/private variable:
  let hitpoints= null;
  
  constructor(name, health=0){
    this.name = name;
    hitpoints= health;
  }
  
  attack(target) {
    // String substitution:
    log(`The monster attacks ${target}`);
  }
  
  get isAlive() {
    return hitpoints > 0;
  }
  
  set health(value) {
    if(value < 0) {
      throw new Error("Health must be non-negative");
    }
    hitpoints= value;
  }
  
}