Small sample for the Mastermind problem solving game

Mastermind.js

class Mastermind {
  constructor() {
    this.answer = [];
    this.blocks = [
      'green',
      'red',
      'blue',
      'yellow',
    ];
  }

  newAnswer() {
    for (let i = 0; i < 4; i++) {
      this.answer[i] = this.blocks[Math.floor(Math.random() * 4)];
    }
  }

  deduce(guess) {
    let blackPegs = 0;
    for (let i = 0; i < 4; i++) {
      if (guess[i] == this.answer[i]) {
        guess[i] = null;
        blackPegs++;
      }
    }
    const whitePegs = Array.from(new Set(guess)).filter(block => this.answer.includes(block)).length;
    if (blackPegs == 4) return 'You win';
    return {
      whitePegs,
      blackPegs,
    }
  }

  guess = (guess) => this.deduce(guess);

}