es2016_decorator.js

function superhero(clazz) {
  Object.defineProperty(clazz.prototype, 'isSuperHero', {value: true});
  return clazz;
}

@superhero
class MySuperHero {
  constructor(first, last) {
    this.name = `${first} ${last}`;
  }
}

let batman = new MySuperHero('Bruce', 'Wayne');
console.log(`${batman.name} is a super hero? ${batman.isSuperHero}`);