ExampleWithoutPolymorphism.js

function Champion(category = 'Champion') {
  this.category = category;
};

function Warrior() {
  Champion.call(this,'Warrior'); 
}
           
function Dwarf() {
  Champion.call(this,'Dwarf'); 
}
        
function Rogue() {
  Champion.call(this,'Rogue'); 
}

// Ugly part you should avoid, based on the above code
const champions = [new Rogue(), new Warrior(), new Dwarf()];

// Using ES6 of
for(hero of champions) {
  if(hero.category == 'Warrior')
    console.log('Hey, a warrior is here');
  else if(hero.category == 'Rogue')
    console.log('Hey, a Rogue is here');
  else
    console.log('Hey, a Dwarf is here');
}

// => Hey, a Rogue is here | Hey, a Warrior is here | Hey, a Dwarf is here