unfairCoin solution

class UnfrairCoin{
    constructor(){
        this.probability = Math.random();
    }
    get(){
        return Math.random() > this.probability ? 1: 0
    }
}

class FairCoin{
    constructor(){
        this.unfairCoin = new UnfrairCoin();
    }
    get(){
       let first = this.unfairCoin.get();
       const unfairCoin = this.unfairCoin;
       let xor = first;
        function helper(){
            const coin = unfairCoin.get();
          if(coin !== first){
              return xor;
          }
          xor ^= 1;
           return helper();
        }
      return helper();
    }
}


var fairCoin = new FairCoin();
var arr = Array.from(Array(1000), ()=>fairCoin.get());
var arr2 = Array.from(Array(1000), () => Math.random() > 0.5 ? 1 : 0);

console.log(fairCoin.unfairCoin.probability, arr.filter(x=>x).length, arr2.filter(x=>x).length);