updateBoard.js

import { List } from 'immutable';

class Game extends Compoent {
  constructor(props) {
    super(props);
    this.generateGame();
  }
  
  generateGame = (finalCount = 20) => {
    // get a filled puzzle generated
    const solution = makePuzzle();
    // pluck values from cells to create the game
    const { puzzle } = pluck(solution, finalCount);
    // initialize the board with choice counts
    const board = makeBoard({ puzzle });
    this.setState({
      board, history: List.of(board), historyOffSet: 0, solution,
    });
  }
  
  updateBoard = (newBoard) => {
    let { history } = this.state;
    const { historyOffSet } = this.state;
    // anything before current step is still in history
    history = history.slice(0, historyOffSet + 1);
    // add itself onto the history
    history = history.push(newBoard);
    // update the game
    this.setState({ board: newBoard, history, historyOffSet: history.size - 1 });
  };
...
}